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

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2025-05-21</periodOfReport>

    <notSubjectToSection16>false</notSubjectToSection16>

    <issuer>
        <issuerCik>0001795815</issuerCik>
        <issuerName>California BanCorp \ CA</issuerName>
        <issuerTradingSymbol>BCAL</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001733127</rptOwnerCik>
            <rptOwnerName>Volk David J.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O CALIFORNIA BANCORP</rptOwnerStreet1>
            <rptOwnerStreet2>355 S. GRAND AVE STE 1200</rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90071</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>true</isDirector>
            <isOfficer>false</isOfficer>
            <isTenPercentOwner>false</isTenPercentOwner>
            <isOther>false</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>false</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2025-05-21</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>false</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>3729.00</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0.00</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2349833.00</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Castle Creek Advisors IV LLC and Castle Creek Capital Partners VI LP</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1195.00</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Options</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>12.96</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2024-02-20</value>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <value>2029-02-20</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>7500.00</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>7500.00</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Options</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>9.67</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2022-03-15</value>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <value>2027-03-15</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>10000.00</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>10000.00</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">These restricted stock units, each of which represents the right to receive one share of common stock of California BanCorp, Inc. (Common Stock), were assigned to Castle Creek Advisors IV LLC (Advisors IV), on behalf of David Volk in his capacity as a member of the Board of Directors of California BanCorp, Inc. and will become fully vested on May 21, 2026.</footnote>
        <footnote id="F2">Includes 6,875 shares of unvested RSUs held by Advisors IV and 2,340,719 shares of Common Stock held by Castle Creek Capital Partners VI LP. Mr. Volk, a managing principal of Castle Creek, disclaims beneficial ownership of such shares held by Advisors IV and Castle Creek Capital Partners VI LP, except to the extent of his pecuniary interest therein and this report shall not be deemed an admission that the reporting person is the beneficial owner of such securities for purposes of Section 16 of the Securities Exchange Act of 1934, as amended, or for any other purpose.</footnote>
        <footnote id="F3">These options are fully vested.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Manisha Merchant, as attorney in fact for Volk David J.</signatureName>
        <signatureDate>2025-05-23</signatureDate>
    </ownerSignature>
</ownershipDocument>
