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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2013-04-01</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001547638</issuerCik>
        <issuerName>Southcross Energy Partners, L.P.</issuerName>
        <issuerTradingSymbol>SXE</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001111641</rptOwnerCik>
            <rptOwnerName>STEINHART RONALD G</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O SOUTHCROSS ENERGY PARTNERS, L.P.</rptOwnerStreet1>
            <rptOwnerStreet2>1700 PACIFIC AVENUE, SUITE 2900</rptOwnerStreet2>
            <rptOwnerCity>DALLAS</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>75201</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText>See Remarks</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Units (Limited Partnership Interest)</value>
            </securityTitle>
            <transactionDate>
                <value>2013-04-01</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>2993</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>25.06</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>7133</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">The reported common units were issued to the Reporting Person pursuant to the Issuer's Non-Employee Director Compensation Arrangement.  Under such arrangement, the Reporting Person received a number of units equivalent to $75,000, divided by a per unit price of $25.06, which is the average of the daily per unit closing price of the Issuer's common units for the 10 trading days immediately before April 1, 2013.</footnote>
    </footnotes>

    <remarks>The Reporting Person is a director of Southcross Energy Partners GP, LLC, the general partner of the Issuer (the &quot;General Partner&quot;). The Issuer is managed by the directors and executive officers of the General Partner.  Exhibit List:  Exhibit 24 - Power of Attorney.</remarks>

    <ownerSignature>
        <signatureName>/s/ Ronald G. Steinhart</signatureName>
        <signatureDate>2013-04-03</signatureDate>
    </ownerSignature>
</ownershipDocument>
