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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2020-05-01</periodOfReport>

    <issuer>
        <issuerCik>0001624322</issuerCik>
        <issuerName>Business First Bancshares, Inc.</issuerName>
        <issuerTradingSymbol>BFST</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001811427</rptOwnerCik>
            <rptOwnerName>Day Rick D.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>500 LAUREL STREET, SUITE 101</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>BATON ROUGE</rptOwnerCity>
            <rptOwnerState>LA</rptOwnerState>
            <rptOwnerZipCode>70801</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2020-05-01</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>237320</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>237320</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Acquired in exchange for 136,000 shares of Pedestal Bancshares, Inc. (&quot;Pedestal&quot;) in connection with the merger of Pedestal with and into the issuer (the &quot;Merger&quot;).  At the effective time of the Merger, each share of Pedestal common stock was converted into the right to receive approximately 1.745 shares of the issuer's common stock.  On the effective date of the Merger, the closing price of the issuer's common stock was $12.96 per share.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Heather Roemer, as attorney-in-fact for Ricky D. Day</signatureName>
        <signatureDate>2020-05-05</signatureDate>
    </ownerSignature>
</ownershipDocument>
