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

    <schemaVersion>X0206</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2021-09-01</periodOfReport>

    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0001013488</issuerCik>
        <issuerName>BJs RESTAURANTS INC</issuerName>
        <issuerTradingSymbol>BJRI</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001878201</rptOwnerCik>
            <rptOwnerName>Houdek Thomas</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>7755 CENTER AVENUE</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 300</rptOwnerStreet2>
            <rptOwnerCity>HUNTINGTON BEACH</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>92647</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>CFO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>10134</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeHolding>
            <securityTitle>
                <value>Non-Qualified Stock Options</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>38.90</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2021-01-15</value>
            </exerciseDate>
            <expirationDate>
                <value>2030-01-15</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>1751</value>
                    <footnoteId id="F2"/>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Non-Qualified Stock Options</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>46.91</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2022-01-15</value>
            </exerciseDate>
            <expirationDate>
                <value>2031-01-15</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>771</value>
                    <footnoteId id="F3"/>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Amount includes 8,269 of unvested Restricted Stock Units, 3,835 vesting in two annual installments beginning October 15, 2021, 314 vesting in two annual installments beginning January 15, 2022, 2,559 vesting in one installment on 1/15/2024, 391 vesting in three annual installments beginning January 15, 2022, and 1,170 vesting in three annual installments beginning September 1, 2022.</footnote>
        <footnote id="F2">Amount includes 584 vested options and 1,167 vesting in two equal annual installments beginning on January 15, 2022</footnote>
        <footnote id="F3">These stock options begin vesting 33.3% per year beginning on January 15, 2022</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Jacob J. Guild, Attorney-in-Fact for Thomas A. Houdek</signatureName>
        <signatureDate>2021-09-03</signatureDate>
    </ownerSignature>
</ownershipDocument>
