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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2014-02-14</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001048477</issuerCik>
        <issuerName>BIOMARIN PHARMACEUTICAL INC</issuerName>
        <issuerTradingSymbol>BMRN</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001557533</rptOwnerCik>
            <rptOwnerName>Ajer Jeffrey Robert</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O BIOMARIN PHARMACEUTICAL INC.,</rptOwnerStreet1>
            <rptOwnerStreet2>770 LINDARO ST.</rptOwnerStreet2>
            <rptOwnerCity>SAN RAFAEL</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94901</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>SVP, Chief Commercial Of</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2014-02-14</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>10500</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>25380</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Represents minimum number of RSUs earned for satisfaction of one of the performance conditions (approval of Vimizin in the U.S. or EU prior to December 31, 2015) for performance-based RSU awards granted under the Issuer's 2006 Share Incentive Plan. The number of shares earned is subject to further adjustment as set forth in the award, based on the Total Shareholder Return (TSR) to be calculated on December 31, 2015.</footnote>
        <footnote id="F2">Although earned, these shares only vest on the filing of the Issuer's Form 10-K for the fiscal year ended December 31, 2015, so long as the reporting person remains continuously employed with the Issuer through that date, subject to earlier vesting upon certain corporate events.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Laura Randall Woodhead, Attorney-in-Fact</signatureName>
        <signatureDate>2014-02-19</signatureDate>
    </ownerSignature>
</ownershipDocument>
