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

    <schemaVersion>X0203</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2009-01-02</periodOfReport>

    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0000356708</issuerCik>
        <issuerName>FIRST REGIONAL BANCORP</issuerName>
        <issuerTradingSymbol>FRGB</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001262623</rptOwnerCik>
            <rptOwnerName>SWEENEY MARILYN J</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>1801 CENTURY PARK EAST</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90067</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>13000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>Held in Reporting Person's IRA</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>229200</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F1"/>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>21003</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Brandon John Trice Irrevocable Trust</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>21003</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Nicholas Akira Sweeney Irrevocable Trust</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>4206</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Jaclyn Yuki Sweeney Irrevocable Trust</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Option</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>7.50</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2009-08-01</value>
                <footnoteId id="F4"/>
            </exerciseDate>
            <expirationDate>
                <value>2018-07-01</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>10000</value>
                    <footnoteId id="F4"/>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Option</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>2.42</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2003-01-01</value>
                <footnoteId id="F5"/>
            </exerciseDate>
            <expirationDate>
                <value>2011-01-31</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>75000</value>
                    <footnoteId id="F5"/>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">19,200 of such shares held directly in the Reporting Person's name.  210,000 of such shares beneficially owned by Reporting Person with Jack A. Sweeney, the Reporting Person's husband, through Trust B of the Sweeney Family Trust U/I 11/13/98.  Does not include shares held by Jack A. Sweeney as his sole and separate property.</footnote>
        <footnote id="F2">The reporting person disclaims beneficial ownership of these shares, and this report shall not be deemed an admission that the Reporting Person is a beneficial owner of such shares for the purpose of Section 16 or for any oher purpose.</footnote>
        <footnote id="F3">Shares beneficially owned by grandchld of Reporting Person's husband, Jack A.Sweeney.  The Reporting Person is the Trustee of this trust.</footnote>
        <footnote id="F4">The option was granted on July 31, 2008 and vests over seven years as follows:  1,400 option shares on August 1 of 2009, 2010, 2011, 2012, 2013 and 2014 and 1,600 option shares on August 1 of 2015.</footnote>
        <footnote id="F5">The option was granted on March 26, 2001 under the Company's 1999 Stock Option Plan and became fully vested on January 1, 2009.</footnote>
    </footnotes>

    <remarks>(6)  The Reporting Person rejoined the board of directors of the issuer on January 2, 2009, as a result of her appointment by the issuer's board to fill the vacancy created by the resignation of Jack A. Sweeney.  The Reporting Person had served as a director of the issuer from February 8, 2001 through May 17, 2005.  In addition, the Reporting Person has continued to serve as a director of the issuer's subsidiary, First Regional Bank, from February 8, 2001 through the present date.  The Reporting Person is the wife of Jack A. Sweeney, the issuer's Founder and Chairman Emeritus, who previously served as Chairman and Chief Executive Officer of the issuer.  Due to such relationship, the Reporting Person was not deemed independent at the time of the issuer's 2005 annual meeting of shareholders and, in order to ensure the independence of a majority of the issuer's board of directors, the Reporting Person did not stand for reelection as a director of the issuer at that time.  Power of attorney filed as Exhibit 24 to Reporting Person's Form 3, filed September 24, 2003.</remarks>

    <ownerSignature>
        <signatureName>Steven J. Sweeney, attorney-in-fact for Marilyn J. Sweeney (6)</signatureName>
        <signatureDate>2009-01-06</signatureDate>
    </ownerSignature>
</ownershipDocument>
