<?xml version="1.0" encoding="us-ascii"?>
<!-- DFIN ActiveDisclosure(SM) XBRL Schema Document - http://www.dfinsolutions.com/ -->
<!-- Creation Date      : 2022-04-27T00:35:18.3354346+00:00 -->
<!-- Version            : 5.0.1.747 -->
<!-- Package ID         : 9318d0d0b6ec4c43a52a8a0f2aab0c68 -->
<!-- Copyright (c) 2022 Donnelley Financial Solutions, Inc. All Rights Reserved. -->
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  <xsd:element id="alks_FundingCommitmentAsPercentageOfPartnershipsFunding" name="FundingCommitmentAsPercentageOfPartnershipsFunding" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" />
  <xsd:element id="alks_EquityMethodCommitment" name="EquityMethodCommitment" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="alks_NumberOfPortfolioSold" name="NumberOfPortfolioSold" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="alks_MarketableSecuritiesRealizedGain" name="MarketableSecuritiesRealizedGain" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="alks_MarketableSecuritiesRealizedLoss" name="MarketableSecuritiesRealizedLoss" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="alks_FairValueRecurringBasisAssetsOrLiabilitiesTransfersBetweenLevelOneToLevelTwo" name="FairValueRecurringBasisAssetsOrLiabilitiesTransfersBetweenLevelOneToLevelTwo" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="alks_FairValueRecurringBasisAssetsOrLiabilitiesTransfersBetweenLevelTwoToLevelOne" name="FairValueRecurringBasisAssetsOrLiabilitiesTransfersBetweenLevelTwoToLevelOne" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="alks_BaudaxBioIncMember" name="BaudaxBioIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="alks_TwentyTwentySixTermLoansMember" name="TwentyTwentySixTermLoansMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="alks_FairValueOfContingentConsiderationMember" name="FairValueOfContingentConsiderationMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="alks_FutureMilestonesReceivableBetween2022And2027" name="FutureMilestonesReceivableBetween2022And2027" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="alks_NumberOfEqualAnnualInstallmentsMilestonePayment" name="NumberOfEqualAnnualInstallmentsMilestonePayment" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" />
  <xsd:element id="alks_MilestonePaymentsReceived" name="MilestonePaymentsReceived" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="alks_MilestonePaymentsReceivable" name="MilestonePaymentsReceivable" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="alks_PercentageOfDiscountRecoveryRate" name="PercentageOfDiscountRecoveryRate" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" />
  <xsd:element id="alks_WeightingPercentageOfDefaultOnObligations" name="WeightingPercentageOfDefaultOnObligations" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="alks_PercentageOfReductionInWorkforcePlanned" name="PercentageOfReductionInWorkforcePlanned" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="alks_InventoryFinishedGoodsNetOfReservesLocatedAtThirdPartyWarehouseAndShippingServiceProvider" name="InventoryFinishedGoodsNetOfReservesLocatedAtThirdPartyWarehouseAndShippingServiceProvider" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="alks_FurnitureFixtureAndEquipmentMember" name="FurnitureFixtureAndEquipmentMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="alks_AccountsPayableAndAccruedExpensesLineItems" name="AccountsPayableAndAccruedExpensesLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="alks_AccountsPayableAndAccruedExpensesTable" name="AccountsPayableAndAccruedExpensesTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="alks_MedicaidRebateMember" name="MedicaidRebateMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="alks_ProductDiscountsMember" name="ProductDiscountsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="alks_MedicarePartDMember" name="MedicarePartDMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="alks_OtherMember" name="OtherMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="alks_DebtInstrumentVariableRateBasisFloor" name="DebtInstrumentVariableRateBasisFloor" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="alks_DebtInstrumentIncrementalCapacitySubjectToSatisfactionOfCertainConditions" name="DebtInstrumentIncrementalCapacitySubjectToSatisfactionOfCertainConditions" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="alks_CommitmentsAndContingenciesLineItems" name="CommitmentsAndContingenciesLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="alks_CommitmentsAndContingenciesTable" name="CommitmentsAndContingenciesTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="alks_JanssenPharmaceuticaNVMember" name="JanssenPharmaceuticaNVMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="alks_NumberOfLicenseAgreementsPartiallyTerminated" name="NumberOfLicenseAgreementsPartiallyTerminated" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="alks_ProceedingsTerminationDate" name="ProceedingsTerminationDate" type="xbrli:dateItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="alks_MaximumPeriodBeforeFDACanApprovePatentRequest" name="MaximumPeriodBeforeFDACanApprovePatentRequest" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
</xsd:schema>
