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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2016-06-24</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001564657</issuerCik>
        <issuerName>NorthStar Real Estate Income II, Inc.</issuerName>
        <issuerTradingSymbol>NONE</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001498420</rptOwnerCik>
            <rptOwnerName>Albro Jonathan Thomas</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O NORTHSTAR REAL ESTATE INCOME II</rptOwnerStreet1>
            <rptOwnerStreet2>399 PARK AVENUE, 18TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10022</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Class A Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2016-06-24</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>3442</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>14442</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Pursuant to the NorthStar Real Estate Income II, Inc. (the &quot;Company&quot;) Second Amended and Restated Independent Directors Compensation Plan (the &quot;Plan&quot;), each of the Company's independent and non-management directors receives a grant of $35,000 in shares of the Company's Class A common stock (the &quot;Restricted Stock&quot;) following re-election to the Company's Board of Directors. The Restricted Stock vests quarterly over a two year period with an initial vesting date of July 1, 2016. Pursuant to the Plan, the amount of Restricted Stock was determined by dividing the fixed grant value of $35,000 by the most recent public offering price per share of the Company's Class A common stock, or $10.1672.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Ronald J. Lieberman, as Attorney-in-Fact for Jonathan T. Albro</signatureName>
        <signatureDate>2016-06-28</signatureDate>
    </ownerSignature>
</ownershipDocument>
