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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4/A</documentType>

    <periodOfReport>2018-03-16</periodOfReport>

    <dateOfOriginalSubmission>2018-03-19</dateOfOriginalSubmission>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001341317</issuerCik>
        <issuerName>Bridgewater Bancshares Inc</issuerName>
        <issuerTradingSymbol>BWB</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001733285</rptOwnerCik>
            <rptOwnerName>Johnson James S.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O BRIDGEWATER BANCSHARES, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>3800 AMERICAN BLVD WEST, SUITE 100</rptOwnerStreet2>
            <rptOwnerCity>BLOOMINGTON</rptOwnerCity>
            <rptOwnerState>MN</rptOwnerState>
            <rptOwnerZipCode>55431</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>158500</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Trust</value>
                    <footnoteId id="F2"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>50416</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By IRA</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>10417</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Spouse IRA</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">On March 19, 2018, the reporting person filed a Form 4 which inadvertently reported that the reporting person beneficially owned 219,333 shares of common stock indirectly by Trust. In fact, as reported in this Amendment, on March 19, 2018 the reporting person beneficially owned 219,333 shares of common stock indirectly (158,500 held by Trust, 50,416 held in the reporting person's IRA and 10,417 held in the IRA of the spouse of the reporting person).</footnote>
        <footnote id="F2">Shares of common stock are held by Mr. Johnson as co-trustee of the James S. Johnson Trust, dated May 28, 2015 and as co-trustee of the Jolynn Johnson Trust dated May 28, 2015. Mr. Johnson possesses shared voting and investment power with respect to the shares of common stock held under the James S. Johnson Trust, dated May 28, 2015 and the Jolynn Johnson Trust dated May 28, 2015</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Ben Klocke, attorney-in-fact</signatureName>
        <signatureDate>2018-11-02</signatureDate>
    </ownerSignature>
</ownershipDocument>
