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

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2009-12-22</periodOfReport>

    <notSubjectToSection16>1</notSubjectToSection16>

    <issuer>
        <issuerCik>0000790202</issuerCik>
        <issuerName>FIRST OPPORTUNITY FUND INC</issuerName>
        <issuerTradingSymbol>FF</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001091477</rptOwnerCik>
            <rptOwnerName>ERNEST HOREJSI TRUST NO 1B</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>1029 WEST 3RD AVENUE, SUITE 400</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>ANCHORAGE</rptOwnerCity>
            <rptOwnerState>AK</rptOwnerState>
            <rptOwnerZipCode>99503</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001246903</rptOwnerCik>
            <rptOwnerName>HOREJSI STEWART R</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>200 SOUTH SANTA FE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SALINA</rptOwnerCity>
            <rptOwnerState>KS</rptOwnerState>
            <rptOwnerZipCode>67401</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001245558</rptOwnerCik>
            <rptOwnerName>CICIORA SUSAN L</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>2344 SPRUCE STREET, STE A</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>BOULDER</rptOwnerCity>
            <rptOwnerState>CO</rptOwnerState>
            <rptOwnerZipCode>80302</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2009-12-22</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>1271426</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>5.98</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                    <footnoteId id="F3"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F2"/>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">The Shares reported in Item 4 were sold at the closing market price of the Fund's stock on December 21, 2009 through a privately negotiated transaction between Trusts affiliated with the Horejsi family.</footnote>
        <footnote id="F2">The trustees of the Ernest Horejsi Trust No. 1B (the &quot;Ernest Trust&quot;) are Alaska Trust Company (&quot;Alaska Trust&quot;), Susan L. Ciciora and Larry Dunlap.  Such trustees may be deemed to control the Ernest Trust and may be deemed to possess indirect beneficial ownership of the Shares held by the Ernest Trust.  However, none of the trustees, acting alone, can vote or exercise dispositive authority over Shares held by the Ernest Trust.  Accordingly, Alaska Trust, Ms. Ciciora and Mr. Dunlap disclaim beneficial ownership of the Shares beneficially owned, directly or indirectly, by the Ernest Trust.  In addition to serving as a trustee, Ms. Ciciora is also a beneficiary of the Ernest Trust.

As a result of his advisory role with the Ernest Trust, Stewart R. Horejsi may be deemed to have indirect beneficial ownership of the Shares directly beneficially owned by the Ernest Trust.  However, Mr. Horejsi disclaims such beneficial ownership of the Shares directly beneficially held by the Ernest Trust.</footnote>
        <footnote id="F3">Trusts affiliated with the Ernest Trust, including the Lola Brown Trust No. 1B, the Mildred B. Horejsi Trust, the Susan L. Ciciora Trust, and the Stewart R. Horejsi Trust No. 2, own an aggregate of 10,204,415 Shares of the Fund following these transactions.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Douglas J. Blattmachr, President, Alaska Trust Company, trustee of the Ernest Horejsi Trust No. 1B</signatureName>
        <signatureDate>2009-12-22</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>Stewart R. Horejsi</signatureName>
        <signatureDate>2009-12-22</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>Susan L. Ciciora</signatureName>
        <signatureDate>2009-12-22</signatureDate>
    </ownerSignature>
</ownershipDocument>
