<?xml version="1.0" encoding="US-ASCII" ?>
    <!-- Field: Doc-Info; Name: Generator; Value: GoFiler Complete; Version: 5.15b -->
    <!-- Field: Doc-Info; Name: VendorURI; Value: https://www.novaworks.com -->
    <!-- Field: Doc-Info; Name: Status; Value: 0x00000000 -->
    <!-- Field: Doc-Info; Name: Misc; Value: 96Mps7xRiXgen8uDanwsWa6C2bP9z5Z86ekhvWBwbdn6bykj8J5BrioVIYh2oXMH -->
<schema xmlns="http://www.w3.org/2001/XMLSchema" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xbrli="http://www.xbrl.org/2003/instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xmlns:xbrldi="http://xbrl.org/2006/xbrldi" xmlns:dei="http://xbrl.sec.gov/dei/2022" xmlns:us-gaap="http://fasb.org/us-gaap/2022" xmlns:srt="http://fasb.org/srt/2022" xmlns:srt-types="http://fasb.org/srt-types/2022" xmlns:dtr-types="http://www.xbrl.org/dtr/type/2020-01-21" xmlns:CLSN="http://celsion.com/20220630" elementFormDefault="qualified" targetNamespace="http://celsion.com/20220630">
    <annotation>
      <appinfo>
	<link:roleType roleURI="http://celsion.com/role/Cover" id="Cover">
	  <link:definition>00000001 - 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 roleURI="http://celsion.com/role/BalanceSheets" id="BalanceSheets">
	  <link:definition>00000002 - Statement - Condensed 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 roleURI="http://celsion.com/role/BalanceSheetsParenthetical" id="BalanceSheetsParenthetical">
	  <link:definition>00000003 - Statement - Condensed 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 roleURI="http://celsion.com/role/StatementsOfOperations" id="StatementsOfOperations">
	  <link:definition>00000004 - Statement - Condensed Consolidated Statements of Operations (Unaudited)</link:definition>
	  <link:usedOn>link:presentationLink</link:usedOn>
	  <link:usedOn>link:calculationLink</link:usedOn>
	  <link:usedOn>link:definitionLink</link:usedOn>
	</link:roleType>
	<link:roleType roleURI="http://celsion.com/role/StatementsOfComprehensiveLoss" id="StatementsOfComprehensiveLoss">
	  <link:definition>00000005 - Statement - Condensed Consolidated Statements of Comprehensive loss (Unaudited)</link:definition>
	  <link:usedOn>link:presentationLink</link:usedOn>
	  <link:usedOn>link:calculationLink</link:usedOn>
	  <link:usedOn>link:definitionLink</link:usedOn>
	</link:roleType>
	<link:roleType roleURI="http://celsion.com/role/StatementsOfCashFlows" id="StatementsOfCashFlows">
	  <link:definition>00000006 - Statement - Condensed Consolidated Statements of Cash Flows (Unaudited)</link:definition>
	  <link:usedOn>link:presentationLink</link:usedOn>
	  <link:usedOn>link:calculationLink</link:usedOn>
	  <link:usedOn>link:definitionLink</link:usedOn>
	</link:roleType>
	<link:roleType roleURI="http://celsion.com/role/StatementsOfChangesInStockholdersEquity" id="StatementsOfChangesInStockholdersEquity">
	  <link:definition>00000007 - Statement - Statements of Changes in Stockholders' Equity (Unaudited)</link:definition>
	  <link:usedOn>link:presentationLink</link:usedOn>
	  <link:usedOn>link:calculationLink</link:usedOn>
	  <link:usedOn>link:definitionLink</link:usedOn>
	</link:roleType>
	<link:roleType roleURI="http://celsion.com/role/BusinessDescription" id="BusinessDescription">
	  <link:definition>00000008 - Disclosure - Business Description</link:definition>
	  <link:usedOn>link:presentationLink</link:usedOn>
	  <link:usedOn>link:calculationLink</link:usedOn>
	  <link:usedOn>link:definitionLink</link:usedOn>
	</link:roleType>
	<link:roleType roleURI="http://celsion.com/role/BasisOfPresentation" id="BasisOfPresentation">
	  <link:definition>00000009 - Disclosure - Basis of Presentation</link:definition>
	  <link:usedOn>link:presentationLink</link:usedOn>
	  <link:usedOn>link:calculationLink</link:usedOn>
	  <link:usedOn>link:definitionLink</link:usedOn>
	</link:roleType>
	<link:roleType roleURI="http://celsion.com/role/NewAccountingPronouncements" id="NewAccountingPronouncements">
	  <link:definition>00000010 - Disclosure - New Accounting Pronouncements</link:definition>
	  <link:usedOn>link:presentationLink</link:usedOn>
	  <link:usedOn>link:calculationLink</link:usedOn>
	  <link:usedOn>link:definitionLink</link:usedOn>
	</link:roleType>
	<link:roleType roleURI="http://celsion.com/role/RestrictedCash" id="RestrictedCash">
	  <link:definition>00000011 - Disclosure - Restricted Cash</link:definition>
	  <link:usedOn>link:presentationLink</link:usedOn>
	  <link:usedOn>link:calculationLink</link:usedOn>
	  <link:usedOn>link:definitionLink</link:usedOn>
	</link:roleType>
	<link:roleType roleURI="http://celsion.com/role/NetLossPerCommonShare" id="NetLossPerCommonShare">
	  <link:definition>00000012 - Disclosure - Net Loss per Common 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 roleURI="http://celsion.com/role/InvestmentInDebtSecurities-availableForSale" id="InvestmentInDebtSecurities-availableForSale">
	  <link:definition>00000013 - Disclosure - Investment in Debt Securities-Available for Sale</link:definition>
	  <link:usedOn>link:presentationLink</link:usedOn>
	  <link:usedOn>link:calculationLink</link:usedOn>
	  <link:usedOn>link:definitionLink</link:usedOn>
	</link:roleType>
	<link:roleType roleURI="http://celsion.com/role/FairValueMeasurements" id="FairValueMeasurements">
	  <link:definition>00000014 - 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 roleURI="http://celsion.com/role/IntangibleAssets" id="IntangibleAssets">
	  <link:definition>00000015 - 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 roleURI="http://celsion.com/role/AccruedLiabilities" id="AccruedLiabilities">
	  <link:definition>00000016 - Disclosure - Accrued Liabilities</link:definition>
	  <link:usedOn>link:presentationLink</link:usedOn>
	  <link:usedOn>link:calculationLink</link:usedOn>
	  <link:usedOn>link:definitionLink</link:usedOn>
	</link:roleType>
	<link:roleType roleURI="http://celsion.com/role/NotesPayable" id="NotesPayable">
	  <link:definition>00000017 - Disclosure - Notes Payable</link:definition>
	  <link:usedOn>link:presentationLink</link:usedOn>
	  <link:usedOn>link:calculationLink</link:usedOn>
	  <link:usedOn>link:definitionLink</link:usedOn>
	</link:roleType>
	<link:roleType roleURI="http://celsion.com/role/StockholdersEquity" id="StockholdersEquity">
	  <link:definition>00000018 - Disclosure - 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 roleURI="http://celsion.com/role/Stock-basedCompensation" id="Stock-basedCompensation">
	  <link:definition>00000019 - 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 roleURI="http://celsion.com/role/Earn-outMilestoneLiability" id="Earn-outMilestoneLiability">
	  <link:definition>00000020 - Disclosure - Earn-Out Milestone Liability</link:definition>
	  <link:usedOn>link:presentationLink</link:usedOn>
	  <link:usedOn>link:calculationLink</link:usedOn>
	  <link:usedOn>link:definitionLink</link:usedOn>
	</link:roleType>
	<link:roleType roleURI="http://celsion.com/role/Warrants" id="Warrants">
	  <link:definition>00000021 - Disclosure - Warrants</link:definition>
	  <link:usedOn>link:presentationLink</link:usedOn>
	  <link:usedOn>link:calculationLink</link:usedOn>
	  <link:usedOn>link:definitionLink</link:usedOn>
	</link:roleType>
	<link:roleType roleURI="http://celsion.com/role/Leases" id="Leases">
	  <link:definition>00000022 - 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 roleURI="http://celsion.com/role/TechnologyDevelopmentAndLicensingAgreements" id="TechnologyDevelopmentAndLicensingAgreements">
	  <link:definition>00000023 - Disclosure - Technology Development and Licensing 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 roleURI="http://celsion.com/role/CommitmentsAndContingencies" id="CommitmentsAndContingencies">
	  <link:definition>00000024 - 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 roleURI="http://celsion.com/role/RestrictedCashTables" id="RestrictedCashTables">
	  <link:definition>00000025 - Disclosure - Restricted Cash (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 roleURI="http://celsion.com/role/InvestmentInDebtSecurities-availableForSaleTables" id="InvestmentInDebtSecurities-availableForSaleTables">
	  <link:definition>00000026 - Disclosure - Investment in Debt Securities-Available for Sale (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 roleURI="http://celsion.com/role/FairValueMeasurementsTables" id="FairValueMeasurementsTables">
	  <link:definition>00000027 - 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 roleURI="http://celsion.com/role/IntangibleAssetsTables" id="IntangibleAssetsTables">
	  <link:definition>00000028 - 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 roleURI="http://celsion.com/role/AccruedLiabilitiesTables" id="AccruedLiabilitiesTables">
	  <link:definition>00000029 - Disclosure - Accrued Liabilities (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 roleURI="http://celsion.com/role/NotesPayableTables" id="NotesPayableTables">
	  <link:definition>00000030 - Disclosure - Notes Payable (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 roleURI="http://celsion.com/role/Stock-basedCompensationTables" id="Stock-basedCompensationTables">
	  <link:definition>00000031 - 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 roleURI="http://celsion.com/role/WarrantsTables" id="WarrantsTables">
	  <link:definition>00000032 - Disclosure - Warrants (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 roleURI="http://celsion.com/role/LeasesTables" id="LeasesTables">
	  <link:definition>00000033 - 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 roleURI="http://celsion.com/role/BasisOfPresentationDetailsNarrative" id="BasisOfPresentationDetailsNarrative">
	  <link:definition>00000034 - Disclosure - Basis of Presentation (Details Narrative)</link:definition>
	  <link:usedOn>link:presentationLink</link:usedOn>
	  <link:usedOn>link:calculationLink</link:usedOn>
	  <link:usedOn>link:definitionLink</link:usedOn>
	</link:roleType>
	<link:roleType roleURI="http://celsion.com/role/ScheduleOfCashAndCashEquivalentsAndRestrictedCashDetails" id="ScheduleOfCashAndCashEquivalentsAndRestrictedCashDetails">
	  <link:definition>00000035 - Disclosure - Schedule of Cash and Cash Equivalents and Restricted Cash (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 roleURI="http://celsion.com/role/RestrictedCashDetailsNarrative" id="RestrictedCashDetailsNarrative">
	  <link:definition>00000036 - Disclosure - Restricted Cash (Details Narrative)</link:definition>
	  <link:usedOn>link:presentationLink</link:usedOn>
	  <link:usedOn>link:calculationLink</link:usedOn>
	  <link:usedOn>link:definitionLink</link:usedOn>
	</link:roleType>
	<link:roleType roleURI="http://celsion.com/role/NetLossPerCommonShareDetailsNarrative" id="NetLossPerCommonShareDetailsNarrative">
	  <link:definition>00000037 - Disclosure - Net Loss per Common Share (Details Narrative)</link:definition>
	  <link:usedOn>link:presentationLink</link:usedOn>
	  <link:usedOn>link:calculationLink</link:usedOn>
	  <link:usedOn>link:definitionLink</link:usedOn>
	</link:roleType>
	<link:roleType roleURI="http://celsion.com/role/ScheduleOfCostFairValueAndMaturitiesOfShortTermInvestmentsDetails" id="ScheduleOfCostFairValueAndMaturitiesOfShortTermInvestmentsDetails">
	  <link:definition>00000038 - Disclosure - Schedule of Cost, Fair Value and Maturities of Short Term Investments (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 roleURI="http://celsion.com/role/SummaryOfInvestmentSecuritiesGrossUnrealizedGainsLossesDetails" id="SummaryOfInvestmentSecuritiesGrossUnrealizedGainsLossesDetails">
	  <link:definition>00000039 - Disclosure - Summary of Investment Securities Gross Unrealized Gains (Losses) (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 roleURI="http://celsion.com/role/SummaryOfInvestmentIncomeDetails" id="SummaryOfInvestmentIncomeDetails">
	  <link:definition>00000040 - Disclosure - Summary of Investment Income (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 roleURI="http://celsion.com/role/InvestmentInDebtSecurities-availableForSaleDetailsNarrative" id="InvestmentInDebtSecurities-availableForSaleDetailsNarrative">
	  <link:definition>00000041 - Disclosure - Investment in Debt Securities-Available for Sale (Details Narrative)</link:definition>
	  <link:usedOn>link:presentationLink</link:usedOn>
	  <link:usedOn>link:calculationLink</link:usedOn>
	  <link:usedOn>link:definitionLink</link:usedOn>
	</link:roleType>
	<link:roleType roleURI="http://celsion.com/role/ScheduleOfFairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisDetails" id="ScheduleOfFairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisDetails">
	  <link:definition>00000042 - Disclosure - Schedule of Fair Value, Assets and Liabilities Measured 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 roleURI="http://celsion.com/role/ScheduleOfFairValueOfAssetsAcquiredDetails" id="ScheduleOfFairValueOfAssetsAcquiredDetails">
	  <link:definition>00000043 - Disclosure - Schedule of Fair Value of Assets Acquired (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 roleURI="http://celsion.com/role/IntangibleAssetsDetailsNarrative" id="IntangibleAssetsDetailsNarrative">
	  <link:definition>00000044 - Disclosure - Intangible Assets (Details Narrative)</link:definition>
	  <link:usedOn>link:presentationLink</link:usedOn>
	  <link:usedOn>link:calculationLink</link:usedOn>
	  <link:usedOn>link:definitionLink</link:usedOn>
	</link:roleType>
	<link:roleType roleURI="http://celsion.com/role/ScheduleOfOtherAccruedLiabilitiesDetails" id="ScheduleOfOtherAccruedLiabilitiesDetails">
	  <link:definition>00000045 - Disclosure - Schedule of Other Accrued 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 roleURI="http://celsion.com/role/ScheduleOfFuturePrinciplePaymentsNetOfUnamortizedDebtDiscountsDetails" id="ScheduleOfFuturePrinciplePaymentsNetOfUnamortizedDebtDiscountsDetails">
	  <link:definition>00000046 - Disclosure - Schedule of Future Principle Payments, Net of Unamortized Debt Discounts (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 roleURI="http://celsion.com/role/ScheduleOfDebtDetails" id="ScheduleOfDebtDetails">
	  <link:definition>00000047 - Disclosure - Schedule of Debt (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 roleURI="http://celsion.com/role/NotesPayableDetailsNarrative" id="NotesPayableDetailsNarrative">
	  <link:definition>00000048 - Disclosure - Notes Payable (Details Narrative)</link:definition>
	  <link:usedOn>link:presentationLink</link:usedOn>
	  <link:usedOn>link:calculationLink</link:usedOn>
	  <link:usedOn>link:definitionLink</link:usedOn>
	</link:roleType>
	<link:roleType roleURI="http://celsion.com/role/StockholdersEquityDetailsNarrative" id="StockholdersEquityDetailsNarrative">
	  <link:definition>00000049 - Disclosure - Stockholders&#8217; Equity (Details Narrative)</link:definition>
	  <link:usedOn>link:presentationLink</link:usedOn>
	  <link:usedOn>link:calculationLink</link:usedOn>
	  <link:usedOn>link:definitionLink</link:usedOn>
	</link:roleType>
	<link:roleType roleURI="http://celsion.com/role/SummaryOfStockOptionAwardsAndRestrictedStockGrantsDetails" id="SummaryOfStockOptionAwardsAndRestrictedStockGrantsDetails">
	  <link:definition>00000050 - Disclosure - Summary of Stock Option Awards and Restricted Stock Grants (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 roleURI="http://celsion.com/role/ScheduleOfAssumptionsUsedToDetermineFairValueOfOptionsGrantedDetails" id="ScheduleOfAssumptionsUsedToDetermineFairValueOfOptionsGrantedDetails">
	  <link:definition>00000051 - Disclosure - Schedule of Assumptions Used to Determine Fair Value of Options Granted (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 roleURI="http://celsion.com/role/Stock-basedCompensationDetailsNarrative" id="Stock-basedCompensationDetailsNarrative">
	  <link:definition>00000052 - Disclosure - Stock-Based Compensation (Details Narrative)</link:definition>
	  <link:usedOn>link:presentationLink</link:usedOn>
	  <link:usedOn>link:calculationLink</link:usedOn>
	  <link:usedOn>link:definitionLink</link:usedOn>
	</link:roleType>
	<link:roleType roleURI="http://celsion.com/role/Earn-outMilestoneLiabilityDetailsNarrative" id="Earn-outMilestoneLiabilityDetailsNarrative">
	  <link:definition>00000053 - Disclosure - Earn-Out Milestone Liability (Details Narrative)</link:definition>
	  <link:usedOn>link:presentationLink</link:usedOn>
	  <link:usedOn>link:calculationLink</link:usedOn>
	  <link:usedOn>link:definitionLink</link:usedOn>
	</link:roleType>
	<link:roleType roleURI="http://celsion.com/role/SummaryOfWarrantActivityDetails" id="SummaryOfWarrantActivityDetails">
	  <link:definition>00000054 - Disclosure - Summary of Warrant 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 roleURI="http://celsion.com/role/ScheduleOfLeasePaymentsAndMaturityOfOperatingLeaseLiabilitiesDetails" id="ScheduleOfLeasePaymentsAndMaturityOfOperatingLeaseLiabilitiesDetails">
	  <link:definition>00000055 - Disclosure - Schedule of Lease Payments and Maturity of Operating Lease 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 roleURI="http://celsion.com/role/LeasesDetailsNarrative" id="LeasesDetailsNarrative">
	  <link:definition>00000056 - Disclosure - Leases (Details Narrative)</link:definition>
	  <link:usedOn>link:presentationLink</link:usedOn>
	  <link:usedOn>link:calculationLink</link:usedOn>
	  <link:usedOn>link:definitionLink</link:usedOn>
	</link:roleType>
	<link:roleType roleURI="http://celsion.com/role/TechnologyDevelopmentAndLicensingAgreementsDetailsNarrative" id="TechnologyDevelopmentAndLicensingAgreementsDetailsNarrative">
	  <link:definition>00000057 - Disclosure - Technology Development and Licensing Agreements (Details Narrative)</link:definition>
	  <link:usedOn>link:presentationLink</link:usedOn>
	  <link:usedOn>link:calculationLink</link:usedOn>
	  <link:usedOn>link:definitionLink</link:usedOn>
	</link:roleType>
	<link:linkbaseRef xlink:type="simple" xlink:href="clsn-20220630_pre.xml" xlink:role="http://www.xbrl.org/2003/role/presentationLinkbaseRef" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:title="Presentation Links" />
	<link:linkbaseRef xlink:type="simple" xlink:href="clsn-20220630_lab.xml" xlink:role="http://www.xbrl.org/2003/role/labelLinkbaseRef" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:title="Label Links" />
	<link:linkbaseRef xlink:type="simple" xlink:href="clsn-20220630_cal.xml" xlink:role="http://www.xbrl.org/2003/role/calculationLinkbaseRef" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:title="Calculation Links" />
	<link:linkbaseRef xlink:type="simple" xlink:href="clsn-20220630_def.xml" xlink:role="http://www.xbrl.org/2003/role/definitionLinkbaseRef" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:title="Definition Links" />
      </appinfo>
    </annotation>
    <import namespace="http://www.xbrl.org/2003/instance" schemaLocation="http://www.xbrl.org/2003/xbrl-instance-2003-12-31.xsd" />
    <import namespace="http://www.xbrl.org/2003/linkbase" schemaLocation="http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd" />
    <import namespace="http://xbrl.sec.gov/dei/2022" schemaLocation="https://xbrl.sec.gov/dei/2022/dei-2022.xsd" />
    <import namespace="http://fasb.org/us-gaap/2022" schemaLocation="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd" />
    <import namespace="http://fasb.org/us-types/2022" schemaLocation="https://xbrl.fasb.org/us-gaap/2022/elts/us-types-2022.xsd" />
    <import namespace="http://www.xbrl.org/dtr/type/2020-01-21" schemaLocation="https://www.xbrl.org/dtr/type/2020-01-21/types.xsd" />
    <import namespace="http://xbrl.sec.gov/country/2022" schemaLocation="https://xbrl.sec.gov/country/2022/country-2022.xsd" />
    <import namespace="http://fasb.org/srt/2022" schemaLocation="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd" />
    <import namespace="http://fasb.org/srt-types/2022" schemaLocation="https://xbrl.fasb.org/srt/2022/elts/srt-types-2022.xsd" />
    <element id="CLSN_SiliconValleyBankMember" name="SiliconValleyBankMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_InprocessRandDMember" name="InprocessRandDMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_EGENIncMember" name="EGENIncMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_IPRAndDDrugTechnologyPlatformsMember" name="IPRAndDDrugTechnologyPlatformsMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_OvarianCancerMember" name="OvarianCancerMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_PurchaseAgreementMember" name="PurchaseAgreementMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_GlioblastomaMultiformeBrainCancerMember" name="GlioblastomaMultiformeBrainCancerMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_IPRAndDMember" name="IPRAndDMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_HorizonCreditAgreementMember" name="HorizonCreditAgreementMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_HorizonTechnologyFinanceCorporationMember" name="HorizonTechnologyFinanceCorporationMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_MarketOfferingAgreementMember" name="MarketOfferingAgreementMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_CapitalOnDemandTMSalesAgreementMember" name="CapitalOnDemandTMSalesAgreementMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_CapitalOnDemandAgreementMember" name="CapitalOnDemandAgreementMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_SecuritiesPurchaseAgreementMember" name="SecuritiesPurchaseAgreementMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_JanuaryRegisteredDirectOfferingMember" name="JanuaryRegisteredDirectOfferingMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_MarchRegisteredDirectOfferingMember" name="MarchRegisteredDirectOfferingMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_SeriesAConvertibleRedeemablePreferredStockMember" name="SeriesAConvertibleRedeemablePreferredStockMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_SeriesBConvertibleRedeemablePreferredStockMember" name="SeriesBConvertibleRedeemablePreferredStockMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_SeriesABPreferredStockMember" name="SeriesABPreferredStockMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_AprilRegisteredDirectOfferingMember" name="AprilRegisteredDirectOfferingMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_TwoThousandAndEighteenStockIncentivePlanMember" name="TwoThousandAndEighteenStockIncentivePlanMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_TwoThousandSevenStockIncentivePlanMember" name="TwoThousandSevenStockIncentivePlanMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_InducementOptionGrantsMember" name="InducementOptionGrantsMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_FiveNewEmployeesMember" name="FiveNewEmployeesMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_EquityStockAwardsMember" name="EquityStockAwardsMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_GrantedUnderTwoThousandEighteenPlanAndTwoThousandSevenPlanMember" name="GrantedUnderTwoThousandEighteenPlanAndTwoThousandSevenPlanMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_TwoThousandAndEighteenPlanMember" name="TwoThousandAndEighteenPlanMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_InducementAwardsMember" name="InducementAwardsMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_EmployeeStockOptionAndRestrictedStockAwardsMember" name="EmployeeStockOptionAndRestrictedStockAwardsMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_AmendedAssetPurchaseAgreementMember" name="AmendedAssetPurchaseAgreementMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_CertainBusinessDaysOfAchievingMilestoneMember" name="CertainBusinessDaysOfAchievingMilestoneMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_EGWCMember" name="EGWCMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_FairValueEarnoutMilestoneLiabilityMember" name="FairValueEarnoutMilestoneLiabilityMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_FirstLeaseAmendmentMember" name="FirstLeaseAmendmentMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_FirstYearMember" name="FirstYearMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_FinalYearMember" name="FinalYearMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_SecondLeaseAmendmentMember" name="SecondLeaseAmendmentMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_EGENAssetPurchaseAgreementMember" name="EGENAssetPurchaseAgreementMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_HuntsvilleAlabamaMember" name="HuntsvilleAlabamaMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_OperatingLeasesMember" name="OperatingLeasesMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_HisunMember" name="HisunMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_GainLossFromChangeInEarnoutMilestoneLiability" name="GainLossFromChangeInEarnoutMilestoneLiability" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_AmortizationOfDeferredFinanceChargesAndDebtDiscountAssociatedWithNotePayable" name="AmortizationOfDeferredFinanceChargesAndDebtDiscountAssociatedWithNotePayable" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_ProceedsFromSvbLoanFacilityNetOfIssuanceCosts" name="ProceedsFromSvbLoanFacilityNetOfIssuanceCosts" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_PayoffOfHorizonAccruedEndOfTermFees" name="PayoffOfHorizonAccruedEndOfTermFees" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_RealizedAndUnrealizedGainsAndLossesNetOnInvestmentInDebtSecurities" name="RealizedAndUnrealizedGainsAndLossesNetOnInvestmentInDebtSecurities" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_SaleOfEquityValueThroughEquityThroughRegisteredDirectOffering" name="SaleOfEquityValueThroughEquityThroughRegisteredDirectOffering" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_SaleOfEquitySharesThroughEquityThroughRegisteredDirectOffering" name="SaleOfEquitySharesThroughEquityThroughRegisteredDirectOffering" nillable="true" xbrli:periodType="duration" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_StockIssuedUponExerciseOfCommonStockWarrants" name="StockIssuedUponExerciseOfCommonStockWarrants" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_StockIssuedUponExerciseOfCommonStockWarrantsShares" name="StockIssuedUponExerciseOfCommonStockWarrantsShares" nillable="true" xbrli:periodType="duration" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_DisclosureFairValueMeasurementsAbstract" name="DisclosureFairValueMeasurementsAbstract" abstract="true" nillable="true" xbrli:periodType="duration" type="xbrli:stringItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_DisclosureEarnoutMilestoneLiabilityAbstract" name="DisclosureEarnoutMilestoneLiabilityAbstract" abstract="true" nillable="true" xbrli:periodType="duration" type="xbrli:stringItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_EarnoutMilestoneLiabilityDisclosureTextBlock" name="EarnoutMilestoneLiabilityDisclosureTextBlock" nillable="true" xbrli:periodType="duration" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_DisclosureWarrantsAbstract" name="DisclosureWarrantsAbstract" abstract="true" nillable="true" xbrli:periodType="duration" type="xbrli:stringItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_WarrantsTextBlock" name="WarrantsTextBlock" nillable="true" xbrli:periodType="duration" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_DisclosureLeasesAbstract" name="DisclosureLeasesAbstract" abstract="true" nillable="true" xbrli:periodType="duration" type="xbrli:stringItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_DisclosureTechnologyDevelopmentAndLicensingAgreementsAbstract" name="DisclosureTechnologyDevelopmentAndLicensingAgreementsAbstract" abstract="true" nillable="true" xbrli:periodType="duration" type="xbrli:stringItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_LicensingTransactionTextBlock" name="LicensingTransactionTextBlock" nillable="true" xbrli:periodType="duration" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_SummaryOfStockOptionAndRestrictedStockAwardsTableTextBlock" name="SummaryOfStockOptionAndRestrictedStockAwardsTableTextBlock" nillable="true" xbrli:periodType="duration" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_DebtSecuritiesAvailableforsaleMaturityAllocatedAndSingleMaturityDateRollingWithinThreeMonthsAmortizedCost" name="DebtSecuritiesAvailableforsaleMaturityAllocatedAndSingleMaturityDateRollingWithinThreeMonthsAmortizedCost" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_DebtSecuritiesAvailableforsaleMaturityAllocatedAndSingleMaturityDateRollingWithinThreeMonthsFairValue" name="DebtSecuritiesAvailableforsaleMaturityAllocatedAndSingleMaturityDateRollingWithinThreeMonthsFairValue" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_DebtSecuritiesAvailableforsaleMaturityAllocatedAndSingleMaturityDateRollingBetweenThreeAndTwelveMonthsAmortizedCost" name="DebtSecuritiesAvailableforsaleMaturityAllocatedAndSingleMaturityDateRollingBetweenThreeAndTwelveMonthsAmortizedCost" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_DebtSecuritiesAvailableforsaleMaturityAllocatedAndSingleMaturityDateRollingBetweenThreeAndTwelveMonthsFairValue" name="DebtSecuritiesAvailableforsaleMaturityAllocatedAndSingleMaturityDateRollingBetweenThreeAndTwelveMonthsFairValue" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_AvailableForSaleDebtSecuritiesAmortizedCostBasisCurrent" name="AvailableForSaleDebtSecuritiesAmortizedCostBasisCurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_AvailableForSaleSecuritiesUnrealizedGainsFairValue" name="AvailableForSaleSecuritiesUnrealizedGainsFairValue" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_AvailableForSaleSecuritiesUnrealizedHoldingGainsLessThanTwelveMonths" name="AvailableForSaleSecuritiesUnrealizedHoldingGainsLessThanTwelveMonths" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_AvailableForSaleSecuritiesUnrealizedLossFairValue" name="AvailableForSaleSecuritiesUnrealizedLossFairValue" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_AvailableForSaleSecuritiesUnrealizedHoldingLossesLessThanTwelveMonths" name="AvailableForSaleSecuritiesUnrealizedHoldingLossesLessThanTwelveMonths" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_AvailableForSaleSecuritiesUnrealizedHoldingGainsLossesLessThanTwelveMonths" name="AvailableForSaleSecuritiesUnrealizedHoldingGainsLossesLessThanTwelveMonths" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_InvestmentIncomeLossNonoperating" name="InvestmentIncomeLossNonoperating" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_NoncashCharge" name="NoncashCharge" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_LongTermDebtMaturitiesRepaymentsOfPrincipalYearFourAndThereAfter" name="LongTermDebtMaturitiesRepaymentsOfPrincipalYearFourAndThereAfter" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_EarlyTerminationFee" name="EarlyTerminationFee" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_EndOfTermCharges" name="EndOfTermCharges" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_FinalPaymentPercentage" name="FinalPaymentPercentage" nillable="true" xbrli:periodType="instant" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_EndOfTermChargePercentage" name="EndOfTermChargePercentage" nillable="true" xbrli:periodType="duration" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_ClassOfWarrantOrRightWarrantsOrRightsCancelled" name="ClassOfWarrantOrRightWarrantsOrRightsCancelled" nillable="true" xbrli:periodType="instant" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_WarrantsDebtLiability" name="WarrantsDebtLiability" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_ShelfRegistrationStatementAmount" name="ShelfRegistrationStatementAmount" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_AggregateOfferingPrices" name="AggregateOfferingPrices" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_PlacementAgentFeeDescription" name="PlacementAgentFeeDescription" nillable="true" xbrli:periodType="duration" type="xbrli:stringItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_PreferredStockStatedValuePerShare" name="PreferredStockStatedValuePerShare" nillable="true" xbrli:periodType="instant" type="dtr-types:perShareItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_InterestExpenseOnPreferredStock" name="InterestExpenseOnPreferredStock" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_StockOptionsStrikePriceDescription" name="StockOptionsStrikePriceDescription" nillable="true" xbrli:periodType="duration" type="xbrli:stringItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_EarnoutMilestoneLiability1" name="EarnoutMilestoneLiability1" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingWeightedAverageExercisePrice" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingWeightedAverageExercisePrice" nillable="true" xbrli:periodType="instant" type="dtr-types:perShareItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsExerciseInPeriodWeightedAverageExercisePrice" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsExerciseInPeriodWeightedAverageExercisePrice" nillable="true" xbrli:periodType="duration" type="dtr-types:perShareItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionsOutstandingIntrinsicValue" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionsOutstandingIntrinsicValue" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_SharebasedCompensationArrangementBySharebasedPaymentAwardNonOptionsOutstandingWeightedAverageRemainingContractualTerm2" name="SharebasedCompensationArrangementBySharebasedPaymentAwardNonOptionsOutstandingWeightedAverageRemainingContractualTerm2" nillable="true" xbrli:periodType="duration" type="xbrli:durationItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearOneAndThereAfter" name="LesseeOperatingLeaseLiabilityPaymentsDueAfterYearOneAndThereAfter" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_DeferredRevenueAmortizationPeriod" name="DeferredRevenueAmortizationPeriod" nillable="true" xbrli:periodType="duration" type="xbrli:durationItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_UpfrontPaymentBeingRecognized" name="UpfrontPaymentBeingRecognized" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_SVBLoanFacilityMember" name="SVBLoanFacilityMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_InitialHorizonCreditAgreementMember" name="InitialHorizonCreditAgreementMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_AmendmentToHorizonCreditAgreementMember" name="AmendmentToHorizonCreditAgreementMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_InitialHorizonCreditAgreementAmendmentMember" name="InitialHorizonCreditAgreementAmendmentMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_AchievingMilestoneWithInOneYearMember" name="AchievingMilestoneWithInOneYearMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_StockIssuedDuringPeriodValueReverseStockSplits" name="StockIssuedDuringPeriodValueReverseStockSplits" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="CLSN_LoanAgreementMember" name="LoanAgreementMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
</schema>
