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

    <schemaVersion>X0304</schemaVersion>

    <documentType>4/A</documentType>

    <periodOfReport>2011-12-02</periodOfReport>

    <dateOfOriginalSubmission>2011-12-02</dateOfOriginalSubmission>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000713095</issuerCik>
        <issuerName>FARMERS CAPITAL BANK CORP</issuerName>
        <issuerTradingSymbol>FFKT</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001237349</rptOwnerCik>
            <rptOwnerName>HILLARD LLOYD C JR</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>POST OFFICE BOX 309</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>FRANKFORT</rptOwnerCity>
            <rptOwnerState>KY</rptOwnerState>
            <rptOwnerZipCode>40602-0309</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>President &amp; CEO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock .125 par value</value>
            </securityTitle>
            <transactionDate>
                <value>2011-12-02</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>3500</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>4.42</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>13903</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">As a result of a key punch error, the Form 4 originally filed on 12/02/2011 incorrectly reported the purchase price. This amended Form 4 is being filed to reflect the correct purchase price.</footnote>
        <footnote id="F2">Of the 13,903 shares owned, 6,788 shares are held in an IRA for the benefit of Mr. Hillard, 575 shares are held in an IRA for the benfit of Mr. Hillard's wife, and 2,000 shares are held in a profit sharing trust for the benefit of Mr. Hillard's wife. These amounts are unchanged from the original Form 4 filed 12/02/2011.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Mark A. Hampton, Attorney in Fact by POA dated 2/3/10</signatureName>
        <signatureDate>2011-12-02</signatureDate>
    </ownerSignature>
</ownershipDocument>
