<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2016-03-17</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000899629</issuerCik>
        <issuerName>ACADIA REALTY TRUST</issuerName>
        <issuerTradingSymbol>AKR</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001218913</rptOwnerCik>
            <rptOwnerName>NAPOLITANO JOSEPH</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O ACADIA REALTY TRUST</rptOwnerStreet1>
            <rptOwnerStreet2>411 THEODORE FREMD AVENUE, SUITE 300</rptOwnerStreet2>
            <rptOwnerCity>RYE</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10580</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Sr. Vice President</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable></nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Limited Partnership Units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>33.65</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2016-03-17</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>20577</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F1"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Shares of Beneficial Interest</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>20577</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>114085</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">On March 17, 2016, Mr. Napolitano was awarded these restricted limited partnership units (&quot;LTIP Units&quot;) in Acadia Realty Limited Partnership (the &quot;Company&quot;).  10,145 LTIP Units shall vest as follows: equal amounts shall vest on January 6, 2017 and on each of the first, second, third and fourth anniversaries thereof, provided that Mr. Napolitano continues to be employed on the vesting date in question.  50% of the remaining 10,432 LTIP Units will vest subject to the same schedule and Mr. Napolitano's continued employment and the other 50% as follows: 60% shall vest on January 6, 2019, subject to Mr. Napolitano's continued employment and the Company achieving certain cumulative benchmarks established by the Company's Board of Trustees.  Provided that the initial 60% vests as described above and further provided that Mr. Napolitano is continuously employed by the Company, 20% shall vest on January 6, 2020 and 20% shall vest on January 6, 2021.</footnote>
        <footnote id="F2">This number represents the total number of LTIP Units (59,063 vested and 55,022 unvested) now held by Mr. Napolitano.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Joseph Napolitano</signatureName>
        <signatureDate>2016-03-21</signatureDate>
    </ownerSignature>
</ownershipDocument>
