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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2017-02-06</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001371446</issuerCik>
        <issuerName>FBR &amp; Co.</issuerName>
        <issuerTradingSymbol>FBRC</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001504216</rptOwnerCik>
            <rptOwnerName>Fishman Adam J</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>1300 NORTH SEVENTEENTH ST.</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 1400</rptOwnerStreet2>
            <rptOwnerCity>ARLINGTON</rptOwnerCity>
            <rptOwnerState>VA</rptOwnerState>
            <rptOwnerZipCode>22209</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Executive Vice President</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2017-02-06</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>8211</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>14.90</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>157617</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Represents shares of the Issuer's common stock withheld to satisfy tax withholding obligations in connection with the delivery of commons tock underlying the vesting of previously awarded restricted stock units (RSUs).</footnote>
        <footnote id="F2">Includes 1,256 shares of the issuer's common stock purchased on June 30, 2016 at a price of $12.793 per share under the issuer's Employee Stock Purchase Plan.</footnote>
        <footnote id="F3">This includes a non-discretionary reallocation of 222 RSUs made on July 1, 2016, 60 RSUs made on October 3, 2016 and 518 RSUs made on January 3, 2017 to the Reporting Person pursuant to the Issuer's 2016 Retention and Incentive Plan under the 2006 Long Term Incentive Plan.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Gavin A. Beske, as Attorney in Fact</signatureName>
        <signatureDate>2017-02-07</signatureDate>
    </ownerSignature>
</ownershipDocument>
