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

    <schemaVersion>X0206</schemaVersion>

    <documentType>3/A</documentType>

    <periodOfReport>2012-09-27</periodOfReport>

    <dateOfOriginalSubmission>2012-10-02</dateOfOriginalSubmission>

    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0001099941</issuerCik>
        <issuerName>MVC CAPITAL, INC.</issuerName>
        <issuerTradingSymbol>MVC</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001067621</rptOwnerCik>
            <rptOwnerName>GOLDSTEIN PHILLIP</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O MVC CAPITAL, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>287 BOWMAN AVE., 2ND FLOOR</rptOwnerStreet2>
            <rptOwnerCity>PURCHASE</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10577</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>45750</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F1"/>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">The Form 3 filed on October 2, 2012 reported that the reporting person held 37,250 common shares directly. The reporting person actually held 45,750 common shares directly. This amended Form 3 is being filed to correctly report the number of common shares held directly by the reporting person.</footnote>
    </footnotes>

    <remarks>See Power of Attorney attached.</remarks>

    <ownerSignature>
        <signatureName>/s/ Stephanie L. Darling, as attorney-in-fact for Phillip Goldstein</signatureName>
        <signatureDate>2014-02-10</signatureDate>
    </ownerSignature>
</ownershipDocument>
