<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with Wdesk from Workiva-->
<!--Copyright 2023 Workiva-->
<!--r:838ae12b-ce84-423c-b3bd-d5043611fe16,g:09a7ef9b-3d5a-4a38-9975-37e1f59f1b78-->
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:arwr="http://www.arrowheadresearch.com/20230331" xmlns:xbrli="http://www.xbrl.org/2003/instance" xmlns:dtr-types="http://www.xbrl.org/dtr/type/2020-01-21" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" attributeFormDefault="unqualified" elementFormDefault="qualified" targetNamespace="http://www.arrowheadresearch.com/20230331">
  <xs:import namespace="http://fasb.org/srt/2022" schemaLocation="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd"/>
  <xs:import namespace="http://fasb.org/us-gaap/2022" schemaLocation="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd"/>
  <xs:import namespace="http://www.w3.org/1999/xlink" schemaLocation="http://www.xbrl.org/2003/xlink-2003-12-31.xsd"/>
  <xs:import namespace="http://www.xbrl.org/2003/instance" schemaLocation="http://www.xbrl.org/2003/xbrl-instance-2003-12-31.xsd"/>
  <xs:import namespace="http://www.xbrl.org/2003/linkbase" schemaLocation="http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd"/>
  <xs:import namespace="http://www.xbrl.org/dtr/type/2020-01-21" schemaLocation="https://www.xbrl.org/dtr/type/2020-01-21/types.xsd"/>
  <xs:import namespace="http://xbrl.org/2005/xbrldt" schemaLocation="http://www.xbrl.org/2005/xbrldt-2005.xsd"/>
  <xs:import namespace="http://xbrl.sec.gov/dei/2022" schemaLocation="https://xbrl.sec.gov/dei/2022/dei-2022.xsd"/>
  <xs:import namespace="http://xbrl.sec.gov/stpr/2022" schemaLocation="https://xbrl.sec.gov/stpr/2022/stpr-2022.xsd"/>
  <xs:annotation>
    <xs:appinfo>
      <link:linkbaseRef xmlns:xlink="http://www.w3.org/1999/xlink" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="arwr-20230331_lab.xml" xlink:role="http://www.xbrl.org/2003/role/labelLinkbaseRef" xlink:type="simple"/>
      <link:linkbaseRef xmlns:xlink="http://www.w3.org/1999/xlink" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="arwr-20230331_pre.xml" xlink:role="http://www.xbrl.org/2003/role/presentationLinkbaseRef" xlink:type="simple"/>
      <link:linkbaseRef xmlns:xlink="http://www.w3.org/1999/xlink" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="arwr-20230331_cal.xml" xlink:role="http://www.xbrl.org/2003/role/calculationLinkbaseRef" xlink:type="simple"/>
      <link:linkbaseRef xmlns:xlink="http://www.w3.org/1999/xlink" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="arwr-20230331_def.xml" xlink:role="http://www.xbrl.org/2003/role/definitionLinkbaseRef" xlink:type="simple"/>
      <link:roleType id="Cover" roleURI="http://www.arrowheadresearch.com/role/Cover">
        <link:definition>0000001 - Document - Cover</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ConsolidatedBalanceSheets" roleURI="http://www.arrowheadresearch.com/role/ConsolidatedBalanceSheets">
        <link:definition>0000002 - Statement - Consolidated Balance Sheets</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ConsolidatedBalanceSheetsParenthetical" roleURI="http://www.arrowheadresearch.com/role/ConsolidatedBalanceSheetsParenthetical">
        <link:definition>0000003 - Statement - Consolidated Balance Sheets (Parenthetical)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ConsolidatedStatementsofOperationsandComprehensiveIncomeLoss" roleURI="http://www.arrowheadresearch.com/role/ConsolidatedStatementsofOperationsandComprehensiveIncomeLoss">
        <link:definition>0000004 - Statement - Consolidated Statements of Operations and Comprehensive Income (Loss)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ConsolidatedStatementsofStockholdersEquity" roleURI="http://www.arrowheadresearch.com/role/ConsolidatedStatementsofStockholdersEquity">
        <link:definition>0000005 - Statement - Consolidated Statements of Stockholders&#8217; Equity</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ConsolidatedStatementsofCashFlows" roleURI="http://www.arrowheadresearch.com/role/ConsolidatedStatementsofCashFlows">
        <link:definition>0000006 - Statement - Consolidated Statements of Cash Flows</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="OrganizationandSignificantAccountingPolicies" roleURI="http://www.arrowheadresearch.com/role/OrganizationandSignificantAccountingPolicies">
        <link:definition>0000007 - Disclosure - Organization and Significant Accounting Policies</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CollaborationandLicenseAgreements" roleURI="http://www.arrowheadresearch.com/role/CollaborationandLicenseAgreements">
        <link:definition>0000008 - Disclosure - Collaboration and License Agreements</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="PropertyandEquipment" roleURI="http://www.arrowheadresearch.com/role/PropertyandEquipment">
        <link:definition>0000009 - Disclosure - Property and Equipment</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="Investments" roleURI="http://www.arrowheadresearch.com/role/Investments">
        <link:definition>0000010 - Disclosure - Investments</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="IntangibleAssets" roleURI="http://www.arrowheadresearch.com/role/IntangibleAssets">
        <link:definition>0000011 - Disclosure - Intangible Assets</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StockholdersEquity" roleURI="http://www.arrowheadresearch.com/role/StockholdersEquity">
        <link:definition>0000012 - Disclosure - Stockholders' Equity</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CommitmentsandContingencies" roleURI="http://www.arrowheadresearch.com/role/CommitmentsandContingencies">
        <link:definition>0000013 - Disclosure - Commitments and Contingencies</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="Leases" roleURI="http://www.arrowheadresearch.com/role/Leases">
        <link:definition>0000014 - Disclosure - Leases</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StockBasedCompensation" roleURI="http://www.arrowheadresearch.com/role/StockBasedCompensation">
        <link:definition>0000015 - Disclosure - Stock-Based Compensation</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="FairValueMeasurements" roleURI="http://www.arrowheadresearch.com/role/FairValueMeasurements">
        <link:definition>0000016 - Disclosure - Fair Value Measurements</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LiabilityRelatedtotheSaleofFutureRoyalties" roleURI="http://www.arrowheadresearch.com/role/LiabilityRelatedtotheSaleofFutureRoyalties">
        <link:definition>0000017 - Disclosure - Liability Related to the Sale of Future Royalties</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EarningsPerShare" roleURI="http://www.arrowheadresearch.com/role/EarningsPerShare">
        <link:definition>0000018 - Disclosure - Earnings Per Share</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="OrganizationandSignificantAccountingPoliciesPolicies" roleURI="http://www.arrowheadresearch.com/role/OrganizationandSignificantAccountingPoliciesPolicies">
        <link:definition>0000019 - Disclosure - Organization and Significant Accounting Policies (Policies)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="OrganizationandSignificantAccountingPoliciesTables" roleURI="http://www.arrowheadresearch.com/role/OrganizationandSignificantAccountingPoliciesTables">
        <link:definition>0000020 - Disclosure - Organization and Significant Accounting Policies (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CollaborationandLicenseAgreementsTables" roleURI="http://www.arrowheadresearch.com/role/CollaborationandLicenseAgreementsTables">
        <link:definition>0000021 - Disclosure - Collaboration and License Agreements (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="PropertyandEquipmentTables" roleURI="http://www.arrowheadresearch.com/role/PropertyandEquipmentTables">
        <link:definition>0000022 - Disclosure - Property and Equipment (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="InvestmentsTables" roleURI="http://www.arrowheadresearch.com/role/InvestmentsTables">
        <link:definition>0000023 - Disclosure - Investments (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="IntangibleAssetsTables" roleURI="http://www.arrowheadresearch.com/role/IntangibleAssetsTables">
        <link:definition>0000024 - Disclosure - Intangible Assets (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StockholdersEquityTables" roleURI="http://www.arrowheadresearch.com/role/StockholdersEquityTables">
        <link:definition>0000025 - Disclosure - Stockholders' Equity (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LeasesTables" roleURI="http://www.arrowheadresearch.com/role/LeasesTables">
        <link:definition>0000026 - Disclosure - Leases (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StockBasedCompensationTables" roleURI="http://www.arrowheadresearch.com/role/StockBasedCompensationTables">
        <link:definition>0000027 - Disclosure - Stock-Based Compensation (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="FairValueMeasurementsTables" roleURI="http://www.arrowheadresearch.com/role/FairValueMeasurementsTables">
        <link:definition>0000028 - Disclosure - Fair Value Measurements (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EarningsPerShareTables" roleURI="http://www.arrowheadresearch.com/role/EarningsPerShareTables">
        <link:definition>0000029 - Disclosure - Earnings Per Share (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="OrganizationandSignificantAccountingPoliciesAdditionalInformationDetail" roleURI="http://www.arrowheadresearch.com/role/OrganizationandSignificantAccountingPoliciesAdditionalInformationDetail">
        <link:definition>0000030 - Disclosure - Organization and Significant Accounting Policies - Additional Information (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CollaborationandLicenseAgreementsRevenueDetails" roleURI="http://www.arrowheadresearch.com/role/CollaborationandLicenseAgreementsRevenueDetails">
        <link:definition>0000031 - Disclosure - Collaboration and License Agreements - Revenue (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CollaborationandLicenseAgreementsReceivablesandContractLiabilitiesDetails" roleURI="http://www.arrowheadresearch.com/role/CollaborationandLicenseAgreementsReceivablesandContractLiabilitiesDetails">
        <link:definition>0000032 - Disclosure - Collaboration and License Agreements - Receivables and Contract Liabilities (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CollaborationandLicenseAgreementsGlaxosmithklineIntellectualPropertyNo3LimitedDetails" roleURI="http://www.arrowheadresearch.com/role/CollaborationandLicenseAgreementsGlaxosmithklineIntellectualPropertyNo3LimitedDetails">
        <link:definition>0000033 - Disclosure - Collaboration and License Agreements - Glaxosmithkline Intellectual Property (No. 3) Limited (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CollaborationandLicenseAgreementsHorizonTherapeuticsIrelandDACDetails" roleURI="http://www.arrowheadresearch.com/role/CollaborationandLicenseAgreementsHorizonTherapeuticsIrelandDACDetails">
        <link:definition>0000034 - Disclosure - Collaboration and License Agreements - Horizon Therapeutics Ireland DAC (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CollaborationandLicenseAgreementsTakedaPharmaceuticalCompanyLimitedDetails" roleURI="http://www.arrowheadresearch.com/role/CollaborationandLicenseAgreementsTakedaPharmaceuticalCompanyLimitedDetails">
        <link:definition>0000035 - Disclosure - Collaboration and License Agreements - Takeda Pharmaceutical Company Limited (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CollaborationandLicenseAgreementsJanssenPharmaceuticalsIncDetails" roleURI="http://www.arrowheadresearch.com/role/CollaborationandLicenseAgreementsJanssenPharmaceuticalsIncDetails">
        <link:definition>0000036 - Disclosure - Collaboration and License Agreements - Janssen Pharmaceuticals, Inc. (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CollaborationandLicenseAgreementsAmgenIncDetails" roleURI="http://www.arrowheadresearch.com/role/CollaborationandLicenseAgreementsAmgenIncDetails">
        <link:definition>0000037 - Disclosure - Collaboration and License Agreements - Amgen, Inc (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CollaborationandLicenseAgreementsJointVentureandLicenseAgreementwithVisirnaTherapeuticsIncDetails" roleURI="http://www.arrowheadresearch.com/role/CollaborationandLicenseAgreementsJointVentureandLicenseAgreementwithVisirnaTherapeuticsIncDetails">
        <link:definition>0000038 - Disclosure - Collaboration and License Agreements - Joint Venture and License Agreement with Visirna Therapeutics, Inc. (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="PropertyandEquipmentSummaryofPropertyandEquipmentDetail" roleURI="http://www.arrowheadresearch.com/role/PropertyandEquipmentSummaryofPropertyandEquipmentDetail">
        <link:definition>0000039 - Disclosure - Property and Equipment - Summary of Property and Equipment (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="PropertyandEquipmentAdditionalInformationDetail" roleURI="http://www.arrowheadresearch.com/role/PropertyandEquipmentAdditionalInformationDetail">
        <link:definition>0000040 - Disclosure - Property and Equipment - Additional Information (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="InvestmentsSummaryofShorttermLongtermInvestmentsandMarketableSecuritiesDetails" roleURI="http://www.arrowheadresearch.com/role/InvestmentsSummaryofShorttermLongtermInvestmentsandMarketableSecuritiesDetails">
        <link:definition>0000041 - Disclosure - Investments - Summary of Short-term, Long-term Investments and Marketable Securities (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="IntangibleAssetsScheduleofIntangibleAssetsDetails" roleURI="http://www.arrowheadresearch.com/role/IntangibleAssetsScheduleofIntangibleAssetsDetails">
        <link:definition>0000042 - Disclosure - Intangible Assets - Schedule of Intangible Assets (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="IntangibleAssetsExpectedFutureAmortizationDetails" roleURI="http://www.arrowheadresearch.com/role/IntangibleAssetsExpectedFutureAmortizationDetails">
        <link:definition>0000043 - Disclosure - Intangible Assets - Expected Future Amortization (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StockholdersEquityDetails" roleURI="http://www.arrowheadresearch.com/role/StockholdersEquityDetails">
        <link:definition>0000044 - Disclosure - Stockholders' Equity (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CommitmentsandContingenciesAdditionalInformationDetail" roleURI="http://www.arrowheadresearch.com/role/CommitmentsandContingenciesAdditionalInformationDetail">
        <link:definition>0000045 - Disclosure - Commitments and Contingencies - Additional Information (Detail)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LeasesNarrativeDetails" roleURI="http://www.arrowheadresearch.com/role/LeasesNarrativeDetails">
        <link:definition>0000046 - Disclosure - Leases - Narrative (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LeasesComponentsofLeaseAssetsandLiabilitiesDetails" roleURI="http://www.arrowheadresearch.com/role/LeasesComponentsofLeaseAssetsandLiabilitiesDetails">
        <link:definition>0000047 - Disclosure - Leases - Components of Lease Assets and Liabilities (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LeasesSummaryofMaturitiesofOperatingLeaseLiabilitiesonanUndiscountedBasisDetails" roleURI="http://www.arrowheadresearch.com/role/LeasesSummaryofMaturitiesofOperatingLeaseLiabilitiesonanUndiscountedBasisDetails">
        <link:definition>0000048 - Disclosure - Leases - Summary of Maturities of Operating Lease Liabilities on an Undiscounted Basis (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LeasesSummaryofMaturitiesofOperatingLeaseLiabilitiesonanUndiscountedBasisDetails_1" roleURI="http://www.arrowheadresearch.com/role/LeasesSummaryofMaturitiesofOperatingLeaseLiabilitiesonanUndiscountedBasisDetails_1">
        <link:definition>0000048 - Disclosure - Leases - Summary of Maturities of Operating Lease Liabilities on an Undiscounted Basis (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LeasesSupplementalCashFlowandOtherInformationRelatedtoLeasesDetails" roleURI="http://www.arrowheadresearch.com/role/LeasesSupplementalCashFlowandOtherInformationRelatedtoLeasesDetails">
        <link:definition>0000049 - Disclosure - Leases - Supplemental Cash Flow and Other Information Related to Leases (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StockBasedCompensationNarrativeDetails" roleURI="http://www.arrowheadresearch.com/role/StockBasedCompensationNarrativeDetails">
        <link:definition>0000050 - Disclosure - Stock-Based Compensation - Narrative (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StockBasedCompensationSummaryofGrantedandOutstandingSharesDetails" roleURI="http://www.arrowheadresearch.com/role/StockBasedCompensationSummaryofGrantedandOutstandingSharesDetails">
        <link:definition>0000051 - Disclosure - Stock-Based Compensation - Summary of Granted and Outstanding Shares (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StockBasedCompensationSummarizeInformationaboutStockOptionsDetails" roleURI="http://www.arrowheadresearch.com/role/StockBasedCompensationSummarizeInformationaboutStockOptionsDetails">
        <link:definition>0000052 - Disclosure - Stock-Based Compensation - Summarize Information about Stock Options (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StockBasedCompensationAssumptionsUsedtoValueStockOptionsDetails" roleURI="http://www.arrowheadresearch.com/role/StockBasedCompensationAssumptionsUsedtoValueStockOptionsDetails">
        <link:definition>0000053 - Disclosure - Stock-Based Compensation - Assumptions Used to Value Stock Options (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StockBasedCompensationSummaryofRSUsActivityDetails" roleURI="http://www.arrowheadresearch.com/role/StockBasedCompensationSummaryofRSUsActivityDetails">
        <link:definition>0000054 - Disclosure - Stock-Based Compensation - Summary of RSUs Activity (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="FairValueMeasurementsFairValueMeasurementsforAssetsandLiabilitiesMeasuredatFairValueonRecurringBasisDetails" roleURI="http://www.arrowheadresearch.com/role/FairValueMeasurementsFairValueMeasurementsforAssetsandLiabilitiesMeasuredatFairValueonRecurringBasisDetails">
        <link:definition>0000055 - Disclosure - Fair Value Measurements - Fair Value Measurements for Assets and Liabilities Measured at Fair Value on Recurring Basis (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LiabilityRelatedtotheSaleofFutureRoyaltiesDetails" roleURI="http://www.arrowheadresearch.com/role/LiabilityRelatedtotheSaleofFutureRoyaltiesDetails">
        <link:definition>0000056 - Disclosure - Liability Related to the Sale of Future Royalties (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EarningsPerShareDetails" roleURI="http://www.arrowheadresearch.com/role/EarningsPerShareDetails">
        <link:definition>0000057 - Disclosure - Earnings Per Share (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
    </xs:appinfo>
  </xs:annotation>
  <xs:element id="arwr_NumberOfAcresOfLandPurchased" abstract="false" name="NumberOfAcresOfLandPurchased" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="arwr_MilestonePaymentReceivableUponFDAApproval" abstract="false" name="MilestonePaymentReceivableUponFDAApproval" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_TaxIncrementFinancingAward" abstract="false" name="TaxIncrementFinancingAward" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_NumberOfDistinctBundle" abstract="false" name="NumberOfDistinctBundle" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="arwr_CommercialMilestonePaymentsAtFirstCommercialSale" abstract="false" name="CommercialMilestonePaymentsAtFirstCommercialSale" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_InitialTransactionPrice" abstract="false" name="InitialTransactionPrice" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_LicenseAgreementMember" abstract="true" name="LicenseAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_SorrentoValleyOwnerDELLCMember" abstract="true" name="SorrentoValleyOwnerDELLCMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_NonCashInterestExpenseLiabilityRelatedToSaleOfFutureRoyalties" abstract="false" name="NonCashInterestExpenseLiabilityRelatedToSaleOfFutureRoyalties" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_NumberOfAgreements" abstract="false" name="NumberOfAgreements" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="arwr_LiabilityRelatedToTheSaleOfFutureRoyaltiesTextBlock" abstract="false" name="LiabilityRelatedToTheSaleOfFutureRoyaltiesTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="arwr_TwoThousandsThirteenIncentivePlanMember" abstract="true" name="TwoThousandsThirteenIncentivePlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_ComputersSoftwareOfficeEquipmentAndFurnitureGross" abstract="false" name="ComputersSoftwareOfficeEquipmentAndFurnitureGross" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_DebtSecuritiesHeldToMaturityAccumulatedUnrecognizedLossNoncurrent" abstract="false" name="DebtSecuritiesHeldToMaturityAccumulatedUnrecognizedLossNoncurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_RoyaltyPaymentThreshold" abstract="false" name="RoyaltyPaymentThreshold" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_AROXDHAgreementMember" abstract="true" name="AROXDHAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_VisirnaTherapeuticsIncMember" abstract="true" name="VisirnaTherapeuticsIncMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_UpfrontMilestonePaymentReceived" abstract="false" name="UpfrontMilestonePaymentReceived" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_HeldToMaturitySecuritiesAndMarketableSecuritiesTableTableTextBlock" abstract="false" name="HeldToMaturitySecuritiesAndMarketableSecuritiesTableTableTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="arwr_LiabilitySaleOfFutureRoyalties" abstract="false" name="LiabilitySaleOfFutureRoyalties" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_LicenseAndCoFundingAgreementMember" abstract="true" name="LicenseAndCoFundingAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_DebtSecuritiesHeldToMaturityAccumulatedUnrecognizedGainNoncurrent" abstract="false" name="DebtSecuritiesHeldToMaturityAccumulatedUnrecognizedGainNoncurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_AmountIntendsToInvestForBuildoutOfFacilities" abstract="false" name="AmountIntendsToInvestForBuildoutOfFacilities" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_JanssenPharmaceuticalsIncorporationMember" abstract="true" name="JanssenPharmaceuticalsIncorporationMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_PercentageOfCommissionOnAggregateGrossProceedsFromSaleOfCommonStock" abstract="false" name="PercentageOfCommissionOnAggregateGrossProceedsFromSaleOfCommonStock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="arwr_CashReceivedAsDueUnderCollaborationAgreement" abstract="false" name="CashReceivedAsDueUnderCollaborationAgreement" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_ResearchFacilityInMadisonMember" abstract="true" name="ResearchFacilityInMadisonMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_NumberOfOptionsToRenew" abstract="false" name="NumberOfOptionsToRenew" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="arwr_ResearchEquipmentGross" abstract="false" name="ResearchEquipmentGross" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_DebtSecuritiesHeldToMaturityAccumulatedUnrecognizedLossCurrent" abstract="false" name="DebtSecuritiesHeldToMaturityAccumulatedUnrecognizedLossCurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_SalesRelatedMilestonePayments" abstract="false" name="SalesRelatedMilestonePayments" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_CommercialNotesMember" abstract="true" name="CommercialNotesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_EstimatedPaymentsForOperatingExpensesYearOne" abstract="false" name="EstimatedPaymentsForOperatingExpensesYearOne" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_HorizonTherapeuticsIrelandDACMember" abstract="true" name="HorizonTherapeuticsIrelandDACMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_NovartisMember" abstract="true" name="NovartisMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_CollaborationAndLicenseAgreementsAbstract" abstract="true" name="CollaborationAndLicenseAgreementsAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="arwr_VeronaTechnologyParkMember" abstract="true" name="VeronaTechnologyParkMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_TwoThousandsFourEquityIncentivePlanMember" abstract="true" name="TwoThousandsFourEquityIncentivePlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_OlpasiranAndAROAMG1AgreementMember" abstract="true" name="OlpasiranAndAROAMG1AgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_ScheduleOfCurrentProductsTableTextBlock" abstract="false" name="ScheduleOfCurrentProductsTableTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="arwr_CommonStockCapitalSharesValueReservedForFutureIssuance" abstract="false" name="CommonStockCapitalSharesValueReservedForFutureIssuance" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_JNJ3989AROHBVAgreementMember" abstract="true" name="JNJ3989AROHBVAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_ScheduleOfHeldToMaturitySecuritiesAndMarketableSecuritiesTable" abstract="true" name="ScheduleOfHeldToMaturitySecuritiesAndMarketableSecuritiesTable" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrldt:hypercubeItem" type="xbrli:stringItemType"/>
  <xs:element id="arwr_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAndEquityInstrumentsOtherThanOptionsOutstanding" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAndEquityInstrumentsOtherThanOptionsOutstanding" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="arwr_CommonStockPurchaseAgreementMember" abstract="true" name="CommonStockPurchaseAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_CollaborationAndLicenseAgreementMember" abstract="true" name="CollaborationAndLicenseAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_GlaxosmithklineIntellectualPropertyLimitedMember" abstract="true" name="GlaxosmithklineIntellectualPropertyLimitedMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_MilestonePayments" abstract="false" name="MilestonePayments" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_TwoThousandFourEquityIncentivePlanTwoThousandThirteenEquityIncentivePlanTwoThousandTwentyOneEquityIncentivePlanAndInducementGrantsMember" abstract="true" name="TwoThousandFourEquityIncentivePlanTwoThousandThirteenEquityIncentivePlanTwoThousandTwentyOneEquityIncentivePlanAndInducementGrantsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_MilestonePaymentReceivableAtStartOfPhaseTwo" abstract="false" name="MilestonePaymentReceivableAtStartOfPhaseTwo" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_RoyaltiesLiabilityNoncurrent" abstract="false" name="RoyaltiesLiabilityNoncurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_TwoThousandTwentyOneIncentivePlanMember" abstract="true" name="TwoThousandTwentyOneIncentivePlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_OrganizationAndSignificantAccountingPoliciesLineItems" abstract="true" name="OrganizationAndSignificantAccountingPoliciesLineItems" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="arwr_PercentageOfEligibleToReceiveTieredRoyaltiesOnNetSales" abstract="false" name="PercentageOfEligibleToReceiveTieredRoyaltiesOnNetSales" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="arwr_TakedaPharmaceuticalsUnitedStatesOfAmericaIncorporatedMember" abstract="true" name="TakedaPharmaceuticalsUnitedStatesOfAmericaIncorporatedMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_DeferredRevenueMember" abstract="true" name="DeferredRevenueMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_JNJ75220795AROJNJ1Member" abstract="true" name="JNJ75220795AROJNJ1Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_ResearchFacilityInSanDiegoMember" abstract="true" name="ResearchFacilityInSanDiegoMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_LaboratoryAndOfficeFacilityMember" abstract="true" name="LaboratoryAndOfficeFacilityMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_MilestonePaymentEarned" abstract="false" name="MilestonePaymentEarned" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_TechnologyLicenseCommitmentsMember" abstract="true" name="TechnologyLicenseCommitmentsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_CorporateHeadquartersInPasadenaMember" abstract="true" name="CorporateHeadquartersInPasadenaMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_VisirnaLicenseAgreementMember" abstract="true" name="VisirnaLicenseAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_FiniteLivedIntangibleAssetsImpairment" abstract="false" name="FiniteLivedIntangibleAssetsImpairment" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_InducementAwardsMember" abstract="true" name="InducementAwardsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_DrugManufacturingFacilityMember" abstract="true" name="DrugManufacturingFacilityMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_HorizonTherapeuticsIrelandDACAndAmgenIncorporatedMember" abstract="true" name="HorizonTherapeuticsIrelandDACAndAmgenIncorporatedMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_DevelopmentRegulatoryAndSalesMilestonesPayments" abstract="false" name="DevelopmentRegulatoryAndSalesMilestonesPayments" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_NumberOfDistinctPerformanceObligations" abstract="false" name="NumberOfDistinctPerformanceObligations" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="arwr_LesseeOperatingLeaseLiabilityPaymentsDueYearFiveAndAfterYearFive" abstract="false" name="LesseeOperatingLeaseLiabilityPaymentsDueYearFiveAndAfterYearFive" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_MilestonePaymentReceivableUponReceiptOfRoyaltyPayments" abstract="false" name="MilestonePaymentReceivableUponReceiptOfRoyaltyPayments" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_OlpasiranAgreementMember" abstract="true" name="OlpasiranAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_FacilitiesMember" abstract="true" name="FacilitiesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_LiabilityRelatedToTheSaleOfFutureRoyaltiesAbstract" abstract="true" name="LiabilityRelatedToTheSaleOfFutureRoyaltiesAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="arwr_FiniteLivedIntangibleAssetExpectedAmortizationAfterYearFour" abstract="false" name="FiniteLivedIntangibleAssetExpectedAmortizationAfterYearFour" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_ScheduleOfHeldToMaturitySecuritiesAndMarketableSecuritiesLineItems" abstract="true" name="ScheduleOfHeldToMaturitySecuritiesAndMarketableSecuritiesLineItems" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="arwr_RoyaltyPharmaAgreementMember" abstract="true" name="RoyaltyPharmaAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_AmgenIncorporatedMember" abstract="true" name="AmgenIncorporatedMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_CashReceivableAsUpfrontPaymentDueUnderCollaborationAgreement" abstract="false" name="CashReceivableAsUpfrontPaymentDueUnderCollaborationAgreement" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_MilestonePaymentReceivableUponAchievementOfPhaseTwoAndFirstPatientDosedInPhaseThree" abstract="false" name="MilestonePaymentReceivableUponAchievementOfPhaseTwoAndFirstPatientDosedInPhaseThree" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_MilestonePaymentReceivable" abstract="false" name="MilestonePaymentReceivable" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_ColoradoOwnerLLCMember" abstract="true" name="ColoradoOwnerLLCMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_AtTheMarketAgreementMember" abstract="true" name="AtTheMarketAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_RoyaltyPharmaMember" abstract="true" name="RoyaltyPharmaMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_MilestonePaymentReceivableUponAchievementOfEnrollmentInPhase3ClinicalTrial" abstract="false" name="MilestonePaymentReceivableUponAchievementOfEnrollmentInPhase3ClinicalTrial" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_DebtSecuritiesHeldToMaturityAccumulatedUnrecognizedGainCurrent" abstract="false" name="DebtSecuritiesHeldToMaturityAccumulatedUnrecognizedGainCurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_JohnsonAndJohnsonInnovationJJDCIncorporationMember" abstract="true" name="JohnsonAndJohnsonInnovationJJDCIncorporationMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="arwr_PaymentsOfLeaseholdImprovementsNetOfTenantImprovementAllowances" abstract="false" name="PaymentsOfLeaseholdImprovementsNetOfTenantImprovementAllowances" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_MilestonePaymentReceived" abstract="false" name="MilestonePaymentReceived" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_IncreaseDecreaseInCashAndInvestments" abstract="false" name="IncreaseDecreaseInCashAndInvestments" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="arwr_OrganizationAndSignificantAccountingPoliciesTable" abstract="true" name="OrganizationAndSignificantAccountingPoliciesTable" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrldt:hypercubeItem" type="xbrli:stringItemType"/>
  <xs:element id="arwr_AdditionalRemainingDevelopmentRegulatoryAndSalesMilestonesPayments" abstract="false" name="AdditionalRemainingDevelopmentRegulatoryAndSalesMilestonesPayments" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
</xs:schema>
