<?xml version="1.0" encoding="US-ASCII"?>
<!--XBRL Document Created with Wdesk from Workiva-->
<!-- -->
<linkbase xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd" xmlns="http://www.xbrl.org/2003/linkbase" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <roleRef roleURI="http://www.commvault.com/role/BasisOfPresentation" xlink:href="cvlt-20150930.xsd#BasisOfPresentation" xlink:type="simple" />
  <roleRef roleURI="http://www.commvault.com/role/Capitalization" xlink:href="cvlt-20150930.xsd#Capitalization" xlink:type="simple" />
  <roleRef roleURI="http://www.commvault.com/role/CapitalizationDetail" xlink:href="cvlt-20150930.xsd#CapitalizationDetail" xlink:type="simple" />
  <roleRef roleURI="http://www.commvault.com/role/CommitmentsAndContingencies" xlink:href="cvlt-20150930.xsd#CommitmentsAndContingencies" xlink:type="simple" />
  <roleRef roleURI="http://www.commvault.com/role/ConsolidatedBalanceSheetsUnaudited" xlink:href="cvlt-20150930.xsd#ConsolidatedBalanceSheetsUnaudited" xlink:type="simple" />
  <roleRef roleURI="http://www.commvault.com/role/ConsolidatedBalanceSheetsUnauditedParenthetical" xlink:href="cvlt-20150930.xsd#ConsolidatedBalanceSheetsUnauditedParenthetical" xlink:type="simple" />
  <roleRef roleURI="http://www.commvault.com/role/ConsolidatedStatementOfStockholdersEquityUnaudited" xlink:href="cvlt-20150930.xsd#ConsolidatedStatementOfStockholdersEquityUnaudited" xlink:type="simple" />
  <roleRef roleURI="http://www.commvault.com/role/ConsolidatedStatementsOfCashFlowsUnaudited" xlink:href="cvlt-20150930.xsd#ConsolidatedStatementsOfCashFlowsUnaudited" xlink:type="simple" />
  <roleRef roleURI="http://www.commvault.com/role/ConsolidatedStatementsOfComprehensiveIncomeLossUnaudited" xlink:href="cvlt-20150930.xsd#ConsolidatedStatementsOfComprehensiveIncomeLossUnaudited" xlink:type="simple" />
  <roleRef roleURI="http://www.commvault.com/role/ConsolidatedStatementsOfIncomeLossUnaudited" xlink:href="cvlt-20150930.xsd#ConsolidatedStatementsOfIncomeLossUnaudited" xlink:type="simple" />
  <roleRef roleURI="http://www.commvault.com/role/DocumentAndEntityInformation" xlink:href="cvlt-20150930.xsd#DocumentAndEntityInformation" xlink:type="simple" />
  <roleRef roleURI="http://www.commvault.com/role/IncomeTaxes" xlink:href="cvlt-20150930.xsd#IncomeTaxes" xlink:type="simple" />
  <roleRef roleURI="http://www.commvault.com/role/IncomeTaxesAdditionalInformationDetail" xlink:href="cvlt-20150930.xsd#IncomeTaxesAdditionalInformationDetail" xlink:type="simple" />
  <roleRef roleURI="http://www.commvault.com/role/IncomeTaxesReconciliationOfAmountsOfUnrecognizedTaxBenefitsDetail" xlink:href="cvlt-20150930.xsd#IncomeTaxesReconciliationOfAmountsOfUnrecognizedTaxBenefitsDetail" xlink:type="simple" />
  <roleRef roleURI="http://www.commvault.com/role/IncomeTaxesTables" xlink:href="cvlt-20150930.xsd#IncomeTaxesTables" xlink:type="simple" />
  <roleRef roleURI="http://www.commvault.com/role/NetIncomeLossPerCommonShare" xlink:href="cvlt-20150930.xsd#NetIncomeLossPerCommonShare" xlink:type="simple" />
  <roleRef roleURI="http://www.commvault.com/role/NetIncomeLossPerCommonShareAdditionalInformationDetail" xlink:href="cvlt-20150930.xsd#NetIncomeLossPerCommonShareAdditionalInformationDetail" xlink:type="simple" />
  <roleRef roleURI="http://www.commvault.com/role/NetIncomeLossPerCommonShareComputationOfBasicAndDilutedNetIncomePerCommonShareDetail" xlink:href="cvlt-20150930.xsd#NetIncomeLossPerCommonShareComputationOfBasicAndDilutedNetIncomePerCommonShareDetail" xlink:type="simple" />
  <roleRef roleURI="http://www.commvault.com/role/NetIncomeLossPerCommonShareTables" xlink:href="cvlt-20150930.xsd#NetIncomeLossPerCommonShareTables" xlink:type="simple" />
  <roleRef roleURI="http://www.commvault.com/role/PropertyAndEquipment" xlink:href="cvlt-20150930.xsd#PropertyAndEquipment" xlink:type="simple" />
  <roleRef roleURI="http://www.commvault.com/role/PropertyAndEquipmentDetail" xlink:href="cvlt-20150930.xsd#PropertyAndEquipmentDetail" xlink:type="simple" />
  <roleRef roleURI="http://www.commvault.com/role/PropertyAndEquipmentTables" xlink:href="cvlt-20150930.xsd#PropertyAndEquipmentTables" xlink:type="simple" />
  <roleRef roleURI="http://www.commvault.com/role/PropertyAndEquipmentTextualDetails" xlink:href="cvlt-20150930.xsd#PropertyAndEquipmentTextualDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.commvault.com/role/RevolvingCreditFacility" xlink:href="cvlt-20150930.xsd#RevolvingCreditFacility" xlink:type="simple" />
  <roleRef roleURI="http://www.commvault.com/role/RevolvingCreditFacilityDetails" xlink:href="cvlt-20150930.xsd#RevolvingCreditFacilityDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.commvault.com/role/StockPlans" xlink:href="cvlt-20150930.xsd#StockPlans" xlink:type="simple" />
  <roleRef roleURI="http://www.commvault.com/role/StockPlansActivityForCompanysTwoStockIncentivePlansDetail" xlink:href="cvlt-20150930.xsd#StockPlansActivityForCompanysTwoStockIncentivePlansDetail" xlink:type="simple" />
  <roleRef roleURI="http://www.commvault.com/role/StockPlansAdditionalInformationDetail" xlink:href="cvlt-20150930.xsd#StockPlansAdditionalInformationDetail" xlink:type="simple" />
  <roleRef roleURI="http://www.commvault.com/role/StockPlansAssumptionsUsedInBlackScholesOptionPricingModelDetail" xlink:href="cvlt-20150930.xsd#StockPlansAssumptionsUsedInBlackScholesOptionPricingModelDetail" xlink:type="simple" />
  <roleRef roleURI="http://www.commvault.com/role/StockPlansEmployeeStockPurchasePlanDetails" xlink:href="cvlt-20150930.xsd#StockPlansEmployeeStockPurchasePlanDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.commvault.com/role/StockPlansRestrictedStockUnitActivityDetail" xlink:href="cvlt-20150930.xsd#StockPlansRestrictedStockUnitActivityDetail" xlink:type="simple" />
  <roleRef roleURI="http://www.commvault.com/role/StockPlansStockBasedCompensationExpenseDetail" xlink:href="cvlt-20150930.xsd#StockPlansStockBasedCompensationExpenseDetail" xlink:type="simple" />
  <roleRef roleURI="http://www.commvault.com/role/StockPlansTables" xlink:href="cvlt-20150930.xsd#StockPlansTables" xlink:type="simple" />
  <roleRef roleURI="http://www.commvault.com/role/SummaryOfSignificantAccountingPolicies" xlink:href="cvlt-20150930.xsd#SummaryOfSignificantAccountingPolicies" xlink:type="simple" />
  <roleRef roleURI="http://www.commvault.com/role/SummaryOfSignificantAccountingPoliciesAdditionalInformationDetail" xlink:href="cvlt-20150930.xsd#SummaryOfSignificantAccountingPoliciesAdditionalInformationDetail" xlink:type="simple" />
  <roleRef roleURI="http://www.commvault.com/role/SummaryOfSignificantAccountingPoliciesDeferredRevenueDetail" xlink:href="cvlt-20150930.xsd#SummaryOfSignificantAccountingPoliciesDeferredRevenueDetail" xlink:type="simple" />
  <roleRef roleURI="http://www.commvault.com/role/SummaryOfSignificantAccountingPoliciesPolicies" xlink:href="cvlt-20150930.xsd#SummaryOfSignificantAccountingPoliciesPolicies" xlink:type="simple" />
  <roleRef roleURI="http://www.commvault.com/role/SummaryOfSignificantAccountingPoliciesSummaryOfFairValueOfFinancialAssetsDetail" xlink:href="cvlt-20150930.xsd#SummaryOfSignificantAccountingPoliciesSummaryOfFairValueOfFinancialAssetsDetail" xlink:type="simple" />
  <roleRef roleURI="http://www.commvault.com/role/SummaryOfSignificantAccountingPoliciesTables" xlink:href="cvlt-20150930.xsd#SummaryOfSignificantAccountingPoliciesTables" xlink:type="simple" />
  <arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all" xlink:type="simple" />
  <arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default" xlink:type="simple" />
  <arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain" xlink:type="simple" />
  <arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member" xlink:type="simple" />
  <arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension" xlink:type="simple" />
  <definitionLink xlink:role="http://www.commvault.com/role/BasisOfPresentation" xlink:type="extended" />
  <definitionLink xlink:role="http://www.commvault.com/role/Capitalization" xlink:type="extended" />
  <definitionLink xlink:role="http://www.commvault.com/role/CapitalizationDetail" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ClassOfStockLineItems" xlink:label="loc_us-gaap_ClassOfStockLineItems_2CBB5BEF10A54E460B97A4E67F58CB64" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ScheduleOfStockByClassTable" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_3E4CEF3DE78E3EBF7EF9A4E67F572D0C" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfStockLineItems_2CBB5BEF10A54E460B97A4E67F58CB64" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_3E4CEF3DE78E3EBF7EF9A4E67F572D0C" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_SubsequentEventTypeAxis" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_1F3517DB71FA65C6FDBCA4E6BBF8617D" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_3E4CEF3DE78E3EBF7EF9A4E67F572D0C" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_1F3517DB71FA65C6FDBCA4E6BBF8617D" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_9FE216ECD4921DDC3E01A4E6BD88CADD_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_1F3517DB71FA65C6FDBCA4E6BBF8617D" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_9FE216ECD4921DDC3E01A4E6BD88CADD_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_9FE216ECD4921DDC3E01A4E6BD88CADD" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_1F3517DB71FA65C6FDBCA4E6BBF8617D" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_9FE216ECD4921DDC3E01A4E6BD88CADD" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_SubsequentEventMember" xlink:label="loc_us-gaap_SubsequentEventMember_5E5A716122BF994D1438A4E6EB0DD2EB" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_9FE216ECD4921DDC3E01A4E6BD88CADD" xlink:to="loc_us-gaap_SubsequentEventMember_5E5A716122BF994D1438A4E6EB0DD2EB" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareRepurchaseProgramAxis" xlink:label="loc_us-gaap_ShareRepurchaseProgramAxis_81D1266FACED2CE499ECA4E67F589B61" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_3E4CEF3DE78E3EBF7EF9A4E67F572D0C" xlink:to="loc_us-gaap_ShareRepurchaseProgramAxis_81D1266FACED2CE499ECA4E67F589B61" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareRepurchaseProgramDomain" xlink:label="loc_us-gaap_ShareRepurchaseProgramDomain_F7F313FA8DA911BF4AF3A4E67F58CFED_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ShareRepurchaseProgramAxis_81D1266FACED2CE499ECA4E67F589B61" xlink:to="loc_us-gaap_ShareRepurchaseProgramDomain_F7F313FA8DA911BF4AF3A4E67F58CFED_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareRepurchaseProgramDomain" xlink:label="loc_us-gaap_ShareRepurchaseProgramDomain_F7F313FA8DA911BF4AF3A4E67F58CFED" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ShareRepurchaseProgramAxis_81D1266FACED2CE499ECA4E67F589B61" xlink:to="loc_us-gaap_ShareRepurchaseProgramDomain_F7F313FA8DA911BF4AF3A4E67F58CFED" xlink:type="arc" />
    <loc xlink:href="cvlt-20150930.xsd#cvlt_CommonStockRepurchaseProgramMember" xlink:label="loc_cvlt_CommonStockRepurchaseProgramMember_D47B6B43DD6FA1421F58A4E67F589C5D" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareRepurchaseProgramDomain_F7F313FA8DA911BF4AF3A4E67F58CFED" xlink:to="loc_cvlt_CommonStockRepurchaseProgramMember_D47B6B43DD6FA1421F58A4E67F589C5D" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_StockRepurchasedDuringPeriodValue" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodValue_0D6D3B20201F95FD4A28A4E67F5892D1" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_2CBB5BEF10A54E460B97A4E67F58CB64" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodValue_0D6D3B20201F95FD4A28A4E67F5892D1" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_StockRepurchasedDuringPeriodShares" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodShares_C5FAF26FCD303C16FBE5A4E67F584FCA" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_2CBB5BEF10A54E460B97A4E67F58CB64" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodShares_C5FAF26FCD303C16FBE5A4E67F584FCA" xlink:type="arc" />
    <loc xlink:href="cvlt-20150930.xsd#cvlt_RepurchaseofCommonStockExpendituresIncurredbutNotyetPaid" xlink:label="loc_cvlt_RepurchaseofCommonStockExpendituresIncurredbutNotyetPaid_5866EFB35A288DAFFB79A4E67F59233E" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_2CBB5BEF10A54E460B97A4E67F58CB64" xlink:to="loc_cvlt_RepurchaseofCommonStockExpendituresIncurredbutNotyetPaid_5866EFB35A288DAFFB79A4E67F59233E" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1" xlink:label="loc_us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1_7130F6D05E6335F906DDA4E67F5992B1" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_2CBB5BEF10A54E460B97A4E67F58CB64" xlink:to="loc_us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1_7130F6D05E6335F906DDA4E67F5992B1" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.commvault.com/role/CommitmentsAndContingencies" xlink:type="extended" />
  <definitionLink xlink:role="http://www.commvault.com/role/ConsolidatedBalanceSheetsUnaudited" xlink:type="extended" />
  <definitionLink xlink:role="http://www.commvault.com/role/ConsolidatedBalanceSheetsUnauditedParenthetical" xlink:type="extended" />
  <definitionLink xlink:role="http://www.commvault.com/role/ConsolidatedStatementOfStockholdersEquityUnaudited" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_us-gaap_StatementLineItems_1796165F5E2AD9F2101581D5FFB53F38" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_StatementTable" xlink:label="loc_us-gaap_StatementTable_252D4730FA238993A1CD81D5FFB58153" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_1796165F5E2AD9F2101581D5FFB53F38" xlink:to="loc_us-gaap_StatementTable_252D4730FA238993A1CD81D5FFB58153" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_FAA9C1B91F41214A5EC681D5FFB543E9" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_252D4730FA238993A1CD81D5FFB58153" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_FAA9C1B91F41214A5EC681D5FFB543E9" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_EFE0FBC1C432ADB9888D81D5FFB5AD94_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_FAA9C1B91F41214A5EC681D5FFB543E9" xlink:to="loc_us-gaap_EquityComponentDomain_EFE0FBC1C432ADB9888D81D5FFB5AD94_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_EFE0FBC1C432ADB9888D81D5FFB5AD94" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_FAA9C1B91F41214A5EC681D5FFB543E9" xlink:to="loc_us-gaap_EquityComponentDomain_EFE0FBC1C432ADB9888D81D5FFB5AD94" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_CommonStockMember" xlink:label="loc_us-gaap_CommonStockMember_AF27791E8C1F10B7B21781D5FFB53F5E" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_EFE0FBC1C432ADB9888D81D5FFB5AD94" xlink:to="loc_us-gaap_CommonStockMember_AF27791E8C1F10B7B21781D5FFB53F5E" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AdditionalPaidInCapitalMember" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_97E1F2D0FA96CC660DB781D5FFB5B34A" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_EFE0FBC1C432ADB9888D81D5FFB5AD94" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_97E1F2D0FA96CC660DB781D5FFB5B34A" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_RetainedEarningsMember" xlink:label="loc_us-gaap_RetainedEarningsMember_E2C6849FAF6740D88DE981D5FFB559FB" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_EFE0FBC1C432ADB9888D81D5FFB5AD94" xlink:to="loc_us-gaap_RetainedEarningsMember_E2C6849FAF6740D88DE981D5FFB559FB" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_AA8B5F37F308A0E5EBAE81D5FFB58903" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_EFE0FBC1C432ADB9888D81D5FFB5AD94" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_AA8B5F37F308A0E5EBAE81D5FFB58903" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_3A5350C3D9DA5D57B0E481D5FFB58354" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_1796165F5E2AD9F2101581D5FFB53F38" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_3A5350C3D9DA5D57B0E481D5FFB58354" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_SharesOutstanding" xlink:label="loc_us-gaap_SharesOutstanding_52EB50C5091687B17F1D81D5FFB543C4" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_3A5350C3D9DA5D57B0E481D5FFB58354" xlink:to="loc_us-gaap_SharesOutstanding_52EB50C5091687B17F1D81D5FFB543C4" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_StockholdersEquity" xlink:label="loc_us-gaap_StockholdersEquity_81B1AEEC44DF31EA038381D5FFB544AB" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_3A5350C3D9DA5D57B0E481D5FFB58354" xlink:to="loc_us-gaap_StockholdersEquity_81B1AEEC44DF31EA038381D5FFB544AB" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_423B027FE0E4CD23AA8D81D5FFB652ED" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_3A5350C3D9DA5D57B0E481D5FFB58354" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_423B027FE0E4CD23AA8D81D5FFB652ED" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalTaxEffectFromShareBasedCompensation" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalTaxEffectFromShareBasedCompensation_DEF2B970EBB358E03F2381D5FFB6C901" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_3A5350C3D9DA5D57B0E481D5FFB58354" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalTaxEffectFromShareBasedCompensation_DEF2B970EBB358E03F2381D5FFB6C901" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_3E50F1797425245229EA81D5FFB651BF" xlink:type="locator" />
    <definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_3A5350C3D9DA5D57B0E481D5FFB58354" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_3E50F1797425245229EA81D5FFB651BF" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_FD3DC5D58F67A66F3B4081D5FFB6ADCC" xlink:type="locator" />
    <definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_3A5350C3D9DA5D57B0E481D5FFB58354" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_FD3DC5D58F67A66F3B4081D5FFB6ADCC" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_StockRepurchasedDuringPeriodShares" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodShares_E1453ED58DBDE796EEED81D5FFB6B4CD" xlink:type="locator" />
    <definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_3A5350C3D9DA5D57B0E481D5FFB58354" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodShares_E1453ED58DBDE796EEED81D5FFB6B4CD" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_StockRepurchasedDuringPeriodValue" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodValue_8AAE621252F912589B8381D5FFB66308" xlink:type="locator" />
    <definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_3A5350C3D9DA5D57B0E481D5FFB58354" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodValue_8AAE621252F912589B8381D5FFB66308" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_NetIncomeLoss" xlink:label="loc_us-gaap_NetIncomeLoss_8AFAD166BD78E753650581D5FFB630DA" xlink:type="locator" />
    <definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_3A5350C3D9DA5D57B0E481D5FFB58354" xlink:to="loc_us-gaap_NetIncomeLoss_8AFAD166BD78E753650581D5FFB630DA" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_28ECC5D00ED1F6F8E96281D5FFB62C14" xlink:type="locator" />
    <definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_3A5350C3D9DA5D57B0E481D5FFB58354" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_28ECC5D00ED1F6F8E96281D5FFB62C14" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.commvault.com/role/ConsolidatedStatementsOfCashFlowsUnaudited" xlink:type="extended" />
  <definitionLink xlink:role="http://www.commvault.com/role/ConsolidatedStatementsOfComprehensiveIncomeLossUnaudited" xlink:type="extended" />
  <definitionLink xlink:role="http://www.commvault.com/role/ConsolidatedStatementsOfIncomeLossUnaudited" xlink:type="extended" />
  <definitionLink xlink:role="http://www.commvault.com/role/DocumentAndEntityInformation" xlink:type="extended" />
  <definitionLink xlink:role="http://www.commvault.com/role/IncomeTaxes" xlink:type="extended" />
  <definitionLink xlink:role="http://www.commvault.com/role/IncomeTaxesAdditionalInformationDetail" xlink:type="extended">
    <loc xlink:href="cvlt-20150930.xsd#cvlt_ReconciliationOfUnrecognizedTaxBenefitsLineItems" xlink:label="loc_cvlt_ReconciliationOfUnrecognizedTaxBenefitsLineItems_21BAB8DF2FA4E839C6F681D5FF24992D" xlink:type="locator" />
    <loc xlink:href="cvlt-20150930.xsd#cvlt_ReconciliationOfUnrecognizedTaxBenefitsTable" xlink:label="loc_cvlt_ReconciliationOfUnrecognizedTaxBenefitsTable_2767F43D96313E7D4D7F81D5FF242A2C" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_cvlt_ReconciliationOfUnrecognizedTaxBenefitsLineItems_21BAB8DF2FA4E839C6F681D5FF24992D" xlink:to="loc_cvlt_ReconciliationOfUnrecognizedTaxBenefitsTable_2767F43D96313E7D4D7F81D5FF242A2C" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_BalanceSheetLocationAxis" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_90848EDB61307F20A0FA81D5FF246CC4" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_cvlt_ReconciliationOfUnrecognizedTaxBenefitsTable_2767F43D96313E7D4D7F81D5FF242A2C" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_90848EDB61307F20A0FA81D5FF246CC4" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_38768CA12E8C17509EFD81D5FF242CC0_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_90848EDB61307F20A0FA81D5FF246CC4" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_38768CA12E8C17509EFD81D5FF242CC0_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_38768CA12E8C17509EFD81D5FF242CC0" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_90848EDB61307F20A0FA81D5FF246CC4" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_38768CA12E8C17509EFD81D5FF242CC0" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_OtherLiabilitiesMember" xlink:label="loc_us-gaap_OtherLiabilitiesMember_271D9D9B8EE166896EE181D5FF2497A3" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_38768CA12E8C17509EFD81D5FF242CC0" xlink:to="loc_us-gaap_OtherLiabilitiesMember_271D9D9B8EE166896EE181D5FF2497A3" xlink:type="arc" />
    <loc xlink:href="cvlt-20150930.xsd#cvlt_DeferredTaxAssetsMember" xlink:label="loc_cvlt_DeferredTaxAssetsMember_F6EFBF2E250ACE99816581D5FF240838" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_38768CA12E8C17509EFD81D5FF242CC0" xlink:to="loc_cvlt_DeferredTaxAssetsMember_F6EFBF2E250ACE99816581D5FF240838" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_UnrecognizedTaxBenefits" xlink:label="loc_us-gaap_UnrecognizedTaxBenefits_352DD354480AC987577B81D5FF247A2E" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cvlt_ReconciliationOfUnrecognizedTaxBenefitsLineItems_21BAB8DF2FA4E839C6F681D5FF24992D" xlink:to="loc_us-gaap_UnrecognizedTaxBenefits_352DD354480AC987577B81D5FF247A2E" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued" xlink:label="loc_us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued_A26B241D6DF8E8B349E681D5FF25EA92" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cvlt_ReconciliationOfUnrecognizedTaxBenefitsLineItems_21BAB8DF2FA4E839C6F681D5FF24992D" xlink:to="loc_us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued_A26B241D6DF8E8B349E681D5FF25EA92" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.commvault.com/role/IncomeTaxesReconciliationOfAmountsOfUnrecognizedTaxBenefitsDetail" xlink:type="extended" />
  <definitionLink xlink:role="http://www.commvault.com/role/IncomeTaxesTables" xlink:type="extended" />
  <definitionLink xlink:role="http://www.commvault.com/role/NetIncomeLossPerCommonShare" xlink:type="extended" />
  <definitionLink xlink:role="http://www.commvault.com/role/NetIncomeLossPerCommonShareAdditionalInformationDetail" xlink:type="extended" />
  <definitionLink xlink:role="http://www.commvault.com/role/NetIncomeLossPerCommonShareComputationOfBasicAndDilutedNetIncomePerCommonShareDetail" xlink:type="extended" />
  <definitionLink xlink:role="http://www.commvault.com/role/NetIncomeLossPerCommonShareTables" xlink:type="extended" />
  <definitionLink xlink:role="http://www.commvault.com/role/PropertyAndEquipment" xlink:type="extended" />
  <definitionLink xlink:role="http://www.commvault.com/role/PropertyAndEquipmentDetail" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_PropertyPlantAndEquipmentLineItems" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_20180DB877CA47323AEA42019B279CCA" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_BEBFFF3CAB9FA60C5DB242019B272E6A" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_20180DB877CA47323AEA42019B279CCA" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_BEBFFF3CAB9FA60C5DB242019B272E6A" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_CA91D54502669955A78F42019B279EFC" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_BEBFFF3CAB9FA60C5DB242019B272E6A" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_CA91D54502669955A78F42019B279EFC" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_EC9CED16644AD8A5A9AD42019B27878F_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_CA91D54502669955A78F42019B279EFC" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_EC9CED16644AD8A5A9AD42019B27878F_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_EC9CED16644AD8A5A9AD42019B27878F" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_CA91D54502669955A78F42019B279EFC" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_EC9CED16644AD8A5A9AD42019B27878F" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_LandMember" xlink:label="loc_us-gaap_LandMember_260FEFE14ADAD1C124CB42019B271423" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_EC9CED16644AD8A5A9AD42019B27878F" xlink:to="loc_us-gaap_LandMember_260FEFE14ADAD1C124CB42019B271423" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_BuildingMember" xlink:label="loc_us-gaap_BuildingMember_65A57162026034C2706D42019B271804" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_EC9CED16644AD8A5A9AD42019B27878F" xlink:to="loc_us-gaap_BuildingMember_65A57162026034C2706D42019B271804" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ComputerEquipmentMember" xlink:label="loc_us-gaap_ComputerEquipmentMember_A5100DFD43052550915242019B27F37C" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_EC9CED16644AD8A5A9AD42019B27878F" xlink:to="loc_us-gaap_ComputerEquipmentMember_A5100DFD43052550915242019B27F37C" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_FurnitureAndFixturesMember" xlink:label="loc_us-gaap_FurnitureAndFixturesMember_441AE1551054672F577542019B271B27" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_EC9CED16644AD8A5A9AD42019B27878F" xlink:to="loc_us-gaap_FurnitureAndFixturesMember_441AE1551054672F577542019B271B27" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_LeaseholdImprovementsMember" xlink:label="loc_us-gaap_LeaseholdImprovementsMember_FB7C320528EBBD0CA3DA42019B279F4B" xlink:type="locator" />
    <definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_EC9CED16644AD8A5A9AD42019B27878F" xlink:to="loc_us-gaap_LeaseholdImprovementsMember_FB7C320528EBBD0CA3DA42019B279F4B" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ComputerSoftwareIntangibleAssetMember" xlink:label="loc_us-gaap_ComputerSoftwareIntangibleAssetMember_B0AB96C3DD04A941E1ED42019B270326" xlink:type="locator" />
    <definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_EC9CED16644AD8A5A9AD42019B27878F" xlink:to="loc_us-gaap_ComputerSoftwareIntangibleAssetMember_B0AB96C3DD04A941E1ED42019B270326" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ConstructionInProgressMember" xlink:label="loc_us-gaap_ConstructionInProgressMember_05261A7C1A3509BCFD5442019B27C3C3" xlink:type="locator" />
    <definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_EC9CED16644AD8A5A9AD42019B27878F" xlink:to="loc_us-gaap_ConstructionInProgressMember_05261A7C1A3509BCFD5442019B27C3C3" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_PropertyPlantAndEquipmentGross" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentGross_9E6C992594A10E8C647642019B27386C" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_20180DB877CA47323AEA42019B279CCA" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentGross_9E6C992594A10E8C647642019B27386C" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment" xlink:label="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_5AA0F0913198C4905B5F42019B274C7E" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_20180DB877CA47323AEA42019B279CCA" xlink:to="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_5AA0F0913198C4905B5F42019B274C7E" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_CA9CD3F03A55431E77F142019B270582" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_20180DB877CA47323AEA42019B279CCA" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_CA9CD3F03A55431E77F142019B270582" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.commvault.com/role/PropertyAndEquipmentTables" xlink:type="extended" />
  <definitionLink xlink:role="http://www.commvault.com/role/PropertyAndEquipmentTextualDetails" xlink:type="extended" />
  <definitionLink xlink:role="http://www.commvault.com/role/RevolvingCreditFacility" xlink:type="extended" />
  <definitionLink xlink:role="http://www.commvault.com/role/RevolvingCreditFacilityDetails" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_LineOfCreditFacilityLineItems" xlink:label="loc_us-gaap_LineOfCreditFacilityLineItems_D8E1503DBB77362C6D3380F755096F3D" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_LineOfCreditFacilityTable" xlink:label="loc_us-gaap_LineOfCreditFacilityTable_919CD9BA30A8DED6276C80F755083FED" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_D8E1503DBB77362C6D3380F755096F3D" xlink:to="loc_us-gaap_LineOfCreditFacilityTable_919CD9BA30A8DED6276C80F755083FED" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_CreditFacilityAxis" xlink:label="loc_us-gaap_CreditFacilityAxis_FF71A7A696B9B814E5B080F75508751D" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_919CD9BA30A8DED6276C80F755083FED" xlink:to="loc_us-gaap_CreditFacilityAxis_FF71A7A696B9B814E5B080F75508751D" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_CreditFacilityDomain" xlink:label="loc_us-gaap_CreditFacilityDomain_5163DCBC1F3CD8A7184180F75509FB03_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_FF71A7A696B9B814E5B080F75508751D" xlink:to="loc_us-gaap_CreditFacilityDomain_5163DCBC1F3CD8A7184180F75509FB03_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_CreditFacilityDomain" xlink:label="loc_us-gaap_CreditFacilityDomain_5163DCBC1F3CD8A7184180F75509FB03" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_FF71A7A696B9B814E5B080F75508751D" xlink:to="loc_us-gaap_CreditFacilityDomain_5163DCBC1F3CD8A7184180F75509FB03" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_RevolvingCreditFacilityMember" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_D4ED84F1F4E7FC51DF7280F75509B398" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_5163DCBC1F3CD8A7184180F75509FB03" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_D4ED84F1F4E7FC51DF7280F75509B398" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_VariableRateAxis" xlink:label="loc_us-gaap_VariableRateAxis_D906102250A96534F72680F755093A38" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_919CD9BA30A8DED6276C80F755083FED" xlink:to="loc_us-gaap_VariableRateAxis_D906102250A96534F72680F755093A38" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_VariableRateDomain" xlink:label="loc_us-gaap_VariableRateDomain_83D534D2FB7C041B4E6680F75509B9BF_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableRateAxis_D906102250A96534F72680F755093A38" xlink:to="loc_us-gaap_VariableRateDomain_83D534D2FB7C041B4E6680F75509B9BF_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_VariableRateDomain" xlink:label="loc_us-gaap_VariableRateDomain_83D534D2FB7C041B4E6680F75509B9BF" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableRateAxis_D906102250A96534F72680F755093A38" xlink:to="loc_us-gaap_VariableRateDomain_83D534D2FB7C041B4E6680F75509B9BF" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_LondonInterbankOfferedRateLIBORMember" xlink:label="loc_us-gaap_LondonInterbankOfferedRateLIBORMember_5B50FA6D84D9EAF8DE6280F755092533" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_83D534D2FB7C041B4E6680F75509B9BF" xlink:to="loc_us-gaap_LondonInterbankOfferedRateLIBORMember_5B50FA6D84D9EAF8DE6280F755092533" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_DebtInstrumentTerm" xlink:label="loc_us-gaap_DebtInstrumentTerm_EF59D7C93C52368F8B7B80F7550978D3" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_D8E1503DBB77362C6D3380F755096F3D" xlink:to="loc_us-gaap_DebtInstrumentTerm_EF59D7C93C52368F8B7B80F7550978D3" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_231A177E5B4ACF46F65480F75509C4C7" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_D8E1503DBB77362C6D3380F755096F3D" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_231A177E5B4ACF46F65480F75509C4C7" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_55A36C499FB7498EE19780F75509B915" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_D8E1503DBB77362C6D3380F755096F3D" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_55A36C499FB7498EE19780F75509B915" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage" xlink:label="loc_us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage_4D3D236048D27C0EADAD80F755098B9D" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_D8E1503DBB77362C6D3380F755096F3D" xlink:to="loc_us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage_4D3D236048D27C0EADAD80F755098B9D" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_UnamortizedDebtIssuanceExpense" xlink:label="loc_us-gaap_UnamortizedDebtIssuanceExpense_8B9A2655332B412E6D9280F755091025" xlink:type="locator" />
    <definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_D8E1503DBB77362C6D3380F755096F3D" xlink:to="loc_us-gaap_UnamortizedDebtIssuanceExpense_8B9A2655332B412E6D9280F755091025" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AmortizationOfFinancingCosts" xlink:label="loc_us-gaap_AmortizationOfFinancingCosts_8F942F5F704D4CA103D080F75509375B" xlink:type="locator" />
    <definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_D8E1503DBB77362C6D3380F755096F3D" xlink:to="loc_us-gaap_AmortizationOfFinancingCosts_8F942F5F704D4CA103D080F75509375B" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.commvault.com/role/StockPlans" xlink:type="extended" />
  <definitionLink xlink:role="http://www.commvault.com/role/StockPlansActivityForCompanysTwoStockIncentivePlansDetail" xlink:type="extended" />
  <definitionLink xlink:role="http://www.commvault.com/role/StockPlansAdditionalInformationDetail" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_1AA9E200183496CAE64E86155C2D1D18" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_F115AC58C7C05B0324B486155C2C33A5" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_1AA9E200183496CAE64E86155C2D1D18" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_F115AC58C7C05B0324B486155C2C33A5" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="loc_us-gaap_AwardTypeAxis_99E272E21E54EE51F97386155C2D2AC2" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_F115AC58C7C05B0324B486155C2C33A5" xlink:to="loc_us-gaap_AwardTypeAxis_99E272E21E54EE51F97386155C2D2AC2" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_F2D6F1788B6B8D1238AF86155C2DA581_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_99E272E21E54EE51F97386155C2D2AC2" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_F2D6F1788B6B8D1238AF86155C2DA581_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_F2D6F1788B6B8D1238AF86155C2DA581" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_99E272E21E54EE51F97386155C2D2AC2" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_F2D6F1788B6B8D1238AF86155C2DA581" xlink:type="arc" />
    <loc xlink:href="cvlt-20150930.xsd#cvlt_StockOptionsandRestrictedStockUnitsMember" xlink:label="loc_cvlt_StockOptionsandRestrictedStockUnitsMember_8F33701B7D00119FE7BF86155C2DFE1F" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_F2D6F1788B6B8D1238AF86155C2DA581" xlink:to="loc_cvlt_StockOptionsandRestrictedStockUnitsMember_8F33701B7D00119FE7BF86155C2DFE1F" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_RestrictedStockUnitsRSUMember" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_F56A97A1029E48E887FC86155C2DC9E1" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_F2D6F1788B6B8D1238AF86155C2DA581" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_F56A97A1029E48E887FC86155C2DC9E1" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_PerformanceSharesMember" xlink:label="loc_us-gaap_PerformanceSharesMember_D7EA61EE6F453DBBECF486155C54F399" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_F2D6F1788B6B8D1238AF86155C2DA581" xlink:to="loc_us-gaap_PerformanceSharesMember_D7EA61EE6F453DBBECF486155C54F399" xlink:type="arc" />
    <loc xlink:href="cvlt-20150930.xsd#cvlt_PerformanceStockOptionsMember" xlink:label="loc_cvlt_PerformanceStockOptionsMember_04F554619A98E3A1747386155C2D161B" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PerformanceSharesMember_D7EA61EE6F453DBBECF486155C54F399" xlink:to="loc_cvlt_PerformanceStockOptionsMember_04F554619A98E3A1747386155C2D161B" xlink:type="arc" />
    <loc xlink:href="cvlt-20150930.xsd#cvlt_PerformanceRestrictedStockUnitsMember" xlink:label="loc_cvlt_PerformanceRestrictedStockUnitsMember_A23AF81B577A0459A4F486155C2D4115" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PerformanceSharesMember_D7EA61EE6F453DBBECF486155C54F399" xlink:to="loc_cvlt_PerformanceRestrictedStockUnitsMember_A23AF81B577A0459A4F486155C2D4115" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_CE7032AB0AA216F51AE286155C2D7065" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_1AA9E200183496CAE64E86155C2D1D18" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_CE7032AB0AA216F51AE286155C2D7065" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_E5BFCBEB6A360D166E6C86155C2D8573" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_1AA9E200183496CAE64E86155C2D1D18" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_E5BFCBEB6A360D166E6C86155C2D8573" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_A72F6F0793420F6D98ED86155C32FA79" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_1AA9E200183496CAE64E86155C2D1D18" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_A72F6F0793420F6D98ED86155C32FA79" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue_CBCBCA896346FD817F3286155C334969" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_1AA9E200183496CAE64E86155C2D1D18" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue_CBCBCA896346FD817F3286155C334969" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_B09A6A0EB0051E4C629586155C330E46" xlink:type="locator" />
    <definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_1AA9E200183496CAE64E86155C2D1D18" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_B09A6A0EB0051E4C629586155C330E46" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_5B9C4567938292B1783486155C337C63" xlink:type="locator" />
    <definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_1AA9E200183496CAE64E86155C2D1D18" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_5B9C4567938292B1783486155C337C63" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_31EDAE643853B6CB31E586155C33DA9E" xlink:type="locator" />
    <definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_1AA9E200183496CAE64E86155C2D1D18" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_31EDAE643853B6CB31E586155C33DA9E" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensation" xlink:label="loc_us-gaap_ShareBasedCompensation_3F2DE0C66AF507A5464286155C331D85" xlink:type="locator" />
    <definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_1AA9E200183496CAE64E86155C2D1D18" xlink:to="loc_us-gaap_ShareBasedCompensation_3F2DE0C66AF507A5464286155C331D85" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.commvault.com/role/StockPlansAssumptionsUsedInBlackScholesOptionPricingModelDetail" xlink:type="extended" />
  <definitionLink xlink:role="http://www.commvault.com/role/StockPlansEmployeeStockPurchasePlanDetails" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_817B8B92DBEEC0EC468981AC76BE6860" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_C5DBFAF6CEA75E7F4F2881AC76BEAFCA" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_817B8B92DBEEC0EC468981AC76BE6860" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_C5DBFAF6CEA75E7F4F2881AC76BEAFCA" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="loc_us-gaap_AwardTypeAxis_A2BC45B7B24EF05D971F81AC76BE0074" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_C5DBFAF6CEA75E7F4F2881AC76BEAFCA" xlink:to="loc_us-gaap_AwardTypeAxis_A2BC45B7B24EF05D971F81AC76BE0074" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_1231BE5B2785102E578B81AC76BEAB73_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_A2BC45B7B24EF05D971F81AC76BE0074" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_1231BE5B2785102E578B81AC76BEAB73_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_1231BE5B2785102E578B81AC76BEAB73" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_A2BC45B7B24EF05D971F81AC76BE0074" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_1231BE5B2785102E578B81AC76BEAB73" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_EmployeeStockMember" xlink:label="loc_us-gaap_EmployeeStockMember_4F7CD22F977D3A68C80181AC76BEC13F" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_1231BE5B2785102E578B81AC76BEAB73" xlink:to="loc_us-gaap_EmployeeStockMember_4F7CD22F977D3A68C80181AC76BEC13F" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent_71F9514FA434BE15F29A81AC76BE3CDA" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_817B8B92DBEEC0EC468981AC76BE6860" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent_71F9514FA434BE15F29A81AC76BE3CDA" xlink:type="arc" />
    <loc xlink:href="cvlt-20150930.xsd#cvlt_SharebasedCompensationArrangementbySharebasedPaymentAwardOfferingPeriod" xlink:label="loc_cvlt_SharebasedCompensationArrangementbySharebasedPaymentAwardOfferingPeriod_F1F17362B23AD0D284C881AC76BE7707" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_817B8B92DBEEC0EC468981AC76BE6860" xlink:to="loc_cvlt_SharebasedCompensationArrangementbySharebasedPaymentAwardOfferingPeriod_F1F17362B23AD0D284C881AC76BE7707" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumEmployeeSubscriptionRate" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumEmployeeSubscriptionRate_BD57973709C0A27350E581AC76BE1CEF" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_817B8B92DBEEC0EC468981AC76BE6860" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumEmployeeSubscriptionRate_BD57973709C0A27350E581AC76BE1CEF" xlink:type="arc" />
    <loc xlink:href="cvlt-20150930.xsd#cvlt_SharebasedCompensationArrangementbySharebasedPaymentAwardMaximumAnnualPurchasesPerEmployeeAmount" xlink:label="loc_cvlt_SharebasedCompensationArrangementbySharebasedPaymentAwardMaximumAnnualPurchasesPerEmployeeAmount_A75B99E72033C08D4B9781AC76BE845D" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_817B8B92DBEEC0EC468981AC76BE6860" xlink:to="loc_cvlt_SharebasedCompensationArrangementbySharebasedPaymentAwardMaximumAnnualPurchasesPerEmployeeAmount_A75B99E72033C08D4B9781AC76BE845D" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_CommonStockCapitalSharesReservedForFutureIssuance" xlink:label="loc_us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_464E22068A77F8B005D981AC76BE818D" xlink:type="locator" />
    <definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_817B8B92DBEEC0EC468981AC76BE6860" xlink:to="loc_us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_464E22068A77F8B005D981AC76BE818D" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AllocatedShareBasedCompensationExpense" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_90042467FB6087C787D381AC76BEF100" xlink:type="locator" />
    <definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_817B8B92DBEEC0EC468981AC76BE6860" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_90042467FB6087C787D381AC76BEF100" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_93C028B6BD7B3E51A9E281AC76BFF8B8" xlink:type="locator" />
    <definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_817B8B92DBEEC0EC468981AC76BE6860" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_93C028B6BD7B3E51A9E281AC76BFF8B8" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.commvault.com/role/StockPlansRestrictedStockUnitActivityDetail" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_A34020678D50CBB4338180F754E65B0B" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_A2D20360532533168CE080F754E5E562" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_A34020678D50CBB4338180F754E65B0B" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_A2D20360532533168CE080F754E5E562" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="loc_us-gaap_AwardTypeAxis_CFF4EC7E926513E28F2F80F754E50D5E" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_A2D20360532533168CE080F754E5E562" xlink:to="loc_us-gaap_AwardTypeAxis_CFF4EC7E926513E28F2F80F754E50D5E" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_22FDCFE898EE8519E10D80F754E5FFC6_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_CFF4EC7E926513E28F2F80F754E50D5E" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_22FDCFE898EE8519E10D80F754E5FFC6_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_22FDCFE898EE8519E10D80F754E5FFC6" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_CFF4EC7E926513E28F2F80F754E50D5E" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_22FDCFE898EE8519E10D80F754E5FFC6" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_RestrictedStockUnitsRSUMember" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_F7D0795526CBF282390380F754E576F5" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_22FDCFE898EE8519E10D80F754E5FFC6" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_F7D0795526CBF282390380F754E576F5" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_1BC6506062CCA8F4DBE580F754E6F8A6" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_A34020678D50CBB4338180F754E65B0B" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_1BC6506062CCA8F4DBE580F754E6F8A6" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_B7BB99D1D033EDB82EA480F754E6EF84" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_1BC6506062CCA8F4DBE580F754E6F8A6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_B7BB99D1D033EDB82EA480F754E6EF84" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_4011E255CBAD8B7F8C3380F754E67AEA" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_1BC6506062CCA8F4DBE580F754E6F8A6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_4011E255CBAD8B7F8C3380F754E67AEA" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_BC1C23AD4EF35A67416080F754E6B9F2" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_1BC6506062CCA8F4DBE580F754E6F8A6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_BC1C23AD4EF35A67416080F754E6B9F2" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_AADE12D3CC743EE9024380F754E66878" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_1BC6506062CCA8F4DBE580F754E6F8A6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_AADE12D3CC743EE9024380F754E66878" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_6D4ADB01A5986435168A80F754E6B552" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_A34020678D50CBB4338180F754E65B0B" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_6D4ADB01A5986435168A80F754E6B552" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_A6000B9CAB04CAC03A9980F754E666E6" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_6D4ADB01A5986435168A80F754E6B552" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_A6000B9CAB04CAC03A9980F754E666E6" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_07ED2E6CF3B91BAEE58980F754E6DCC7" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_6D4ADB01A5986435168A80F754E6B552" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_07ED2E6CF3B91BAEE58980F754E6DCC7" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_5ABF51DB8C176FB8746A80F754E65ACA" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_6D4ADB01A5986435168A80F754E6B552" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_5ABF51DB8C176FB8746A80F754E65ACA" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_12D707450788D0F976B980F754E6AEA0" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_6D4ADB01A5986435168A80F754E6B552" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_12D707450788D0F976B980F754E6AEA0" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.commvault.com/role/StockPlansStockBasedCompensationExpenseDetail" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_366CF70E75003B7C770B80F754FBB0B4" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable" xlink:label="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_2606C809B8ACD680AF1680F754FBB7FA" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_366CF70E75003B7C770B80F754FBB0B4" xlink:to="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_2606C809B8ACD680AF1680F754FBB7FA" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_IncomeStatementLocationAxis" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_618A5D372204861D5A0F80F754FB5CE5" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_2606C809B8ACD680AF1680F754FBB7FA" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_618A5D372204861D5A0F80F754FB5CE5" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_9AFE457F06636B02124880F754FB332B_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_618A5D372204861D5A0F80F754FB5CE5" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_9AFE457F06636B02124880F754FB332B_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_9AFE457F06636B02124880F754FB332B" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_618A5D372204861D5A0F80F754FB5CE5" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_9AFE457F06636B02124880F754FB332B" xlink:type="arc" />
    <loc xlink:href="cvlt-20150930.xsd#cvlt_CostOfServicesRevenueMember" xlink:label="loc_cvlt_CostOfServicesRevenueMember_22BFBD8F0917DC28B9F080F754FB0D54" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_9AFE457F06636B02124880F754FB332B" xlink:to="loc_cvlt_CostOfServicesRevenueMember_22BFBD8F0917DC28B9F080F754FB0D54" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_SellingAndMarketingExpenseMember" xlink:label="loc_us-gaap_SellingAndMarketingExpenseMember_31FD5DCC40217B36A3F180F754FBC75C" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_9AFE457F06636B02124880F754FB332B" xlink:to="loc_us-gaap_SellingAndMarketingExpenseMember_31FD5DCC40217B36A3F180F754FBC75C" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ResearchAndDevelopmentExpenseMember" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpenseMember_F7624509EC904AEB61E280F754FB0ABF" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_9AFE457F06636B02124880F754FB332B" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpenseMember_F7624509EC904AEB61E280F754FB0ABF" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_GeneralAndAdministrativeExpenseMember" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpenseMember_0CD25A3A8CB78DDF261A80F754FB71A5" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_9AFE457F06636B02124880F754FB332B" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpenseMember_0CD25A3A8CB78DDF261A80F754FB71A5" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ShareBasedCompensation" xlink:label="loc_us-gaap_ShareBasedCompensation_CDA961303D215E242A3780F754FB33F0" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_366CF70E75003B7C770B80F754FBB0B4" xlink:to="loc_us-gaap_ShareBasedCompensation_CDA961303D215E242A3780F754FB33F0" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.commvault.com/role/StockPlansTables" xlink:type="extended" />
  <definitionLink xlink:role="http://www.commvault.com/role/SummaryOfSignificantAccountingPolicies" xlink:type="extended" />
  <definitionLink xlink:role="http://www.commvault.com/role/SummaryOfSignificantAccountingPoliciesAdditionalInformationDetail" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ConcentrationRiskLineItems" xlink:label="loc_us-gaap_ConcentrationRiskLineItems_CB178A5D6B7C9FB3D647A4E734278254" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ConcentrationRiskTable" xlink:label="loc_us-gaap_ConcentrationRiskTable_3BB170DF2F8B149E7CD8A4E734275085" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_CB178A5D6B7C9FB3D647A4E734278254" xlink:to="loc_us-gaap_ConcentrationRiskTable_3BB170DF2F8B149E7CD8A4E734275085" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_LegalEntityAxis" xlink:label="loc_dei_LegalEntityAxis_CCF999596D2F7DA4BA58A4E734273035" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_3BB170DF2F8B149E7CD8A4E734275085" xlink:to="loc_dei_LegalEntityAxis_CCF999596D2F7DA4BA58A4E734273035" xlink:type="arc" />
    <loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_EntityDomain" xlink:label="loc_dei_EntityDomain_4976F5C9D5D3443C5745A4E734277B88_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_CCF999596D2F7DA4BA58A4E734273035" xlink:to="loc_dei_EntityDomain_4976F5C9D5D3443C5745A4E734277B88_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_EntityDomain" xlink:label="loc_dei_EntityDomain_4976F5C9D5D3443C5745A4E734277B88" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_CCF999596D2F7DA4BA58A4E734273035" xlink:to="loc_dei_EntityDomain_4976F5C9D5D3443C5745A4E734277B88" xlink:type="arc" />
    <loc xlink:href="cvlt-20150930.xsd#cvlt_ArrowMember" xlink:label="loc_cvlt_ArrowMember_B81A336B47A7D33EB10EA4E734272D5F" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_4976F5C9D5D3443C5745A4E734277B88" xlink:to="loc_cvlt_ArrowMember_B81A336B47A7D33EB10EA4E734272D5F" xlink:type="arc" />
    <loc xlink:href="cvlt-20150930.xsd#cvlt_HitachiMember" xlink:label="loc_cvlt_HitachiMember_FDDDBEBD80A75FA755C2A4E73427D4FA" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_4976F5C9D5D3443C5745A4E734277B88" xlink:to="loc_cvlt_HitachiMember_FDDDBEBD80A75FA755C2A4E73427D4FA" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_9503546E9E31265BB515A4E734277CEB" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_3BB170DF2F8B149E7CD8A4E734275085" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_9503546E9E31265BB515A4E734277CEB" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_E806E13AE00A8BA099F7A4E73427B148_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_9503546E9E31265BB515A4E734277CEB" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_E806E13AE00A8BA099F7A4E73427B148_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_E806E13AE00A8BA099F7A4E73427B148" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_9503546E9E31265BB515A4E734277CEB" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_E806E13AE00A8BA099F7A4E73427B148" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_SalesRevenueNetMember" xlink:label="loc_us-gaap_SalesRevenueNetMember_180F73AAB6F645DE0D10A4E734279C06" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_E806E13AE00A8BA099F7A4E73427B148" xlink:to="loc_us-gaap_SalesRevenueNetMember_180F73AAB6F645DE0D10A4E734279C06" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_AccountsReceivableMember" xlink:label="loc_us-gaap_AccountsReceivableMember_F91744D078EFBC0F0542A4E73427275C" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_E806E13AE00A8BA099F7A4E73427B148" xlink:to="loc_us-gaap_AccountsReceivableMember_F91744D078EFBC0F0542A4E73427275C" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_ConcentrationRiskPercentage1" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_711F2B451F87BAFAEA9EA4E73427B1AD" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_CB178A5D6B7C9FB3D647A4E734278254" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_711F2B451F87BAFAEA9EA4E73427B1AD" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.commvault.com/role/SummaryOfSignificantAccountingPoliciesDeferredRevenueDetail" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_DeferredRevenueArrangementLineItems" xlink:label="loc_us-gaap_DeferredRevenueArrangementLineItems_59C87A057D1B692A8CF880F75526DB90" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_DeferredRevenueArrangementByTypeTable" xlink:label="loc_us-gaap_DeferredRevenueArrangementByTypeTable_76E434D4FDCFFC28CF6880F75526C784" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DeferredRevenueArrangementLineItems_59C87A057D1B692A8CF880F75526DB90" xlink:to="loc_us-gaap_DeferredRevenueArrangementByTypeTable_76E434D4FDCFFC28CF6880F75526C784" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_DeferredRevenueArrangementTypeAxis" xlink:label="loc_us-gaap_DeferredRevenueArrangementTypeAxis_4781DECC28D6891066DA80F755265D92" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DeferredRevenueArrangementByTypeTable_76E434D4FDCFFC28CF6880F75526C784" xlink:to="loc_us-gaap_DeferredRevenueArrangementTypeAxis_4781DECC28D6891066DA80F755265D92" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_DeferredRevenueArrangementTypeDomain" xlink:label="loc_us-gaap_DeferredRevenueArrangementTypeDomain_5202B788AE979CA6CC0680F755260740_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DeferredRevenueArrangementTypeAxis_4781DECC28D6891066DA80F755265D92" xlink:to="loc_us-gaap_DeferredRevenueArrangementTypeDomain_5202B788AE979CA6CC0680F755260740_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_DeferredRevenueArrangementTypeDomain" xlink:label="loc_us-gaap_DeferredRevenueArrangementTypeDomain_5202B788AE979CA6CC0680F755260740" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DeferredRevenueArrangementTypeAxis_4781DECC28D6891066DA80F755265D92" xlink:to="loc_us-gaap_DeferredRevenueArrangementTypeDomain_5202B788AE979CA6CC0680F755260740" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_SoftwareLicenseArrangementMember" xlink:label="loc_us-gaap_SoftwareLicenseArrangementMember_CE00702A32BA869A4D7B80F75526C808" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredRevenueArrangementTypeDomain_5202B788AE979CA6CC0680F755260740" xlink:to="loc_us-gaap_SoftwareLicenseArrangementMember_CE00702A32BA869A4D7B80F75526C808" xlink:type="arc" />
    <loc xlink:href="cvlt-20150930.xsd#cvlt_DeferredServicesRevenueMember" xlink:label="loc_cvlt_DeferredServicesRevenueMember_FF5582E1590A0E02C85180F755263512" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredRevenueArrangementTypeDomain_5202B788AE979CA6CC0680F755260740" xlink:to="loc_cvlt_DeferredServicesRevenueMember_FF5582E1590A0E02C85180F755263512" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_DeferredRevenueCurrent" xlink:label="loc_us-gaap_DeferredRevenueCurrent_7C73854997520EE2C27780F755260E36" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredRevenueArrangementLineItems_59C87A057D1B692A8CF880F75526DB90" xlink:to="loc_us-gaap_DeferredRevenueCurrent_7C73854997520EE2C27780F755260E36" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_DeferredRevenueNoncurrent" xlink:label="loc_us-gaap_DeferredRevenueNoncurrent_BD287361D5FF9ACA920C80F755262948" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredRevenueArrangementLineItems_59C87A057D1B692A8CF880F75526DB90" xlink:to="loc_us-gaap_DeferredRevenueNoncurrent_BD287361D5FF9ACA920C80F755262948" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_DeferredRevenue" xlink:label="loc_us-gaap_DeferredRevenue_72E381910246E22008A380F75526DBA3" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredRevenueArrangementLineItems_59C87A057D1B692A8CF880F75526DB90" xlink:to="loc_us-gaap_DeferredRevenue_72E381910246E22008A380F75526DBA3" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.commvault.com/role/SummaryOfSignificantAccountingPoliciesPolicies" xlink:type="extended" />
  <definitionLink xlink:role="http://www.commvault.com/role/SummaryOfSignificantAccountingPoliciesSummaryOfFairValueOfFinancialAssetsDetail" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_732B7F065164EA0AE8B880F75522F880" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_A582220CC3E54F6B023380F7552271A9" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_732B7F065164EA0AE8B880F75522F880" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_A582220CC3E54F6B023380F7552271A9" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_DCCA27D67EC57348267C80F755220A2B" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_A582220CC3E54F6B023380F7552271A9" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_DCCA27D67EC57348267C80F755220A2B" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_CA32DFD888EB994BB24C80F755229BCE_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_DCCA27D67EC57348267C80F755220A2B" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_CA32DFD888EB994BB24C80F755229BCE_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_CA32DFD888EB994BB24C80F755229BCE" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_DCCA27D67EC57348267C80F755220A2B" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_CA32DFD888EB994BB24C80F755229BCE" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_FairValueInputsLevel1Member" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_E59F737260CA3930A23D80F75522762B" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_CA32DFD888EB994BB24C80F755229BCE" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_E59F737260CA3930A23D80F75522762B" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_FairValueInputsLevel2Member" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_AFAB572CEE985D025DBD80F755220A17" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_CA32DFD888EB994BB24C80F755229BCE" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_AFAB572CEE985D025DBD80F755220A17" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_FairValueInputsLevel3Member" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_89BCA8A73B885D5D6D3B80F75522F6FC" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_CA32DFD888EB994BB24C80F755229BCE" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_89BCA8A73B885D5D6D3B80F75522F6FC" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_CashAndCashEquivalentsFairValueDisclosure" xlink:label="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_D8263B781F6B7B01EFD580F75522E61B" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_732B7F065164EA0AE8B880F75522F880" xlink:to="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_D8263B781F6B7B01EFD580F75522E61B" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2015/elts/us-gaap-2015-01-31.xsd#us-gaap_HeldToMaturitySecuritiesFairValue" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesFairValue_356BB05D1E69B791654480F7552227B0" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_732B7F065164EA0AE8B880F75522F880" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesFairValue_356BB05D1E69B791654480F7552227B0" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.commvault.com/role/SummaryOfSignificantAccountingPoliciesTables" xlink:type="extended" />
</linkbase>
