<SUBMISSION>
<ACCESSION-NUMBER>0001365555-12-000016
<TYPE>4
<PUBLIC-DOCUMENT-COUNT>1
<PERIOD>20121003
<FILING-DATE>20121005
<DATE-OF-FILING-DATE-CHANGE>20121005
<REPORTING-OWNER>
<OWNER-DATA>
<CONFORMED-NAME>SAKS DAVID
<CIK>0001464765
</OWNER-DATA>
<FILING-VALUES>
<FORM-TYPE>4
<ACT>34
<FILE-NUMBER>001-33143
<FILM-NUMBER>121131976
</FILING-VALUES>
<MAIL-ADDRESS>
<STREET1>59 MAIDEN LANE
<CITY>NEW YORK
<STATE>NY
<ZIP>10038
</MAIL-ADDRESS>
</REPORTING-OWNER>
<ISSUER>
<COMPANY-DATA>
<CONFORMED-NAME>Amtrust Financial Services, Inc.
<CIK>0001365555
<ASSIGNED-SIC>6331
<IRS-NUMBER>043106389
<STATE-OF-INCORPORATION>DE
<FISCAL-YEAR-END>1231
</COMPANY-DATA>
<BUSINESS-ADDRESS>
<STREET1>59 MAIDEN LANE
<STREET2>6TH FLOOR
<CITY>NEW YORK
<STATE>NY
<ZIP>10038
<PHONE>(212) 220-7120
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>59 MAIDEN LANE
<STREET2>6TH FLOOR
<CITY>NEW YORK
<STATE>NY
<ZIP>10038
</MAIL-ADDRESS>
</ISSUER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>wf-form4_134946155603866.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2012-10-03</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001365555</issuerCik>
        <issuerName>Amtrust Financial Services, Inc.</issuerName>
        <issuerTradingSymbol>AFSI</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001464765</rptOwnerCik>
            <rptOwnerName>SAKS DAVID</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O AMTRUST FINANCIAL SERVICES, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>59 MAIDEN LANE, 6TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10038</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Chief Legal Officer</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2012-10-03</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>320</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2979</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2012-10-03</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>114</value>
                    <footnoteId id="F3"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>25.31</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2865</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Restricted Stock Units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F4"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2012-10-03</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>320</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F5"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F5"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>320.0</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>961</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F6"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Acquisition of common stock resulting from the vesting of one-fourth of the restricted stock units granted to Mr. Saks on October 3, 2011.</footnote>
        <footnote id="F2">On August 6, 2012, AmTrust Financial Services, Inc. declared a 10% stock dividend payable on September 20, 2012 to all holders of record of common stock as of September 4, 2012. As a result, Mr. Saks received 241 shares of AmTrust Financial Services, Inc. common stock on September 20, 2012.</footnote>
        <footnote id="F3">Disposition of common stock resulting from the withholding of securities for the payment of tax liability relating to the vesting of one-fourth of the restricted stock units granted to Mr. Saks on October 3, 2011.</footnote>
        <footnote id="F4">Each restricted stock unit represents a contingent right to receive one share of AmTrust Financial Services, Inc.'s common stock.</footnote>
        <footnote id="F5">On October 3, 2011, Mr. Saks received restricted stock units subject to a four-year vesting schedule, vesting 25% on the first, second, third and fourth anniversaries of the grant date.  As restricted stock units vest, the vested units are automatically converted to vested common stock on a one-for-one basis on the vesting date.</footnote>
        <footnote id="F6">Pursuant to anti-dilution provisions in AmTrust Financial Services, Inc.'s 2010 Omnibus Incentive Plan, 1,164 restricted stock units granted to Mr. Saks on October 3, 2011 and held on September 20, 2012 became 1,281 restricted stock units.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ David Saks</signatureName>
        <signatureDate>2012-10-05</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SUBMISSION>
