<?xml version="1.0"?>
<ownershipDocument>
    <schemaVersion>X0201</schemaVersion>

    <documentType>4</documentType>
<periodOfReport>2003-12-22</periodOfReport>
<notSubjectToSection16>0</notSubjectToSection16>
    <issuer>
        <issuerCik>0000353567</issuerCik>
        <issuerName>ICO INC</issuerName>
        <issuerTradingSymbol>ICOC</issuerTradingSymbol>
</issuer>
<reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001220920</rptOwnerCik>
            <rptOwnerName>KNAPP A JOHN JR</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>910 TRAVIS STREET, SUITE 1900</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>HOUSTON</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>77002</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
<isDirector>1</isDirector>
<isOfficer>0</isOfficer>
<isTenPercentOwner>0</isTenPercentOwner>
<isOther>0</isOther>
<officerTitle></officerTitle>
<otherText></otherText>
</reportingOwnerRelationship>
</reportingOwner>
<nonDerivativeTable>
<nonDerivativeTransaction>
<securityTitle>
<value>Common Stock</value>
</securityTitle>
<transactionDate>
<value>2003-12-22</value>
</transactionDate>
<deemedExecutionDate>
</deemedExecutionDate>
<transactionCoding>
<transactionFormType>4</transactionFormType>
<transactionCode>P</transactionCode>
<equitySwapInvolved>0</equitySwapInvolved>
</transactionCoding>
<transactionTimeliness>
<value></value>
</transactionTimeliness>
<transactionAmounts>
<transactionShares>
<value>26750</value>
</transactionShares>
<transactionPricePerShare>
<value>1.17</value>
</transactionPricePerShare>
<transactionAcquiredDisposedCode>
<value>A</value>
</transactionAcquiredDisposedCode>
</transactionAmounts>
<postTransactionAmounts>
<sharesOwnedFollowingTransaction>
<value>286293</value>
<footnoteId id="F1"/>
</sharesOwnedFollowingTransaction>
</postTransactionAmounts>
<ownershipNature>
<directOrIndirectOwnership>
<value>D</value>
</directOrIndirectOwnership>
<natureOfOwnership>
<value></value>
</natureOfOwnership>
</ownershipNature>
</nonDerivativeTransaction>
</nonDerivativeTable>
<footnotes>
<footnote id="F1">Individual owns 1,687,134 shares indirectly which are held by Travis Street Partners LLC</footnote>
</footnotes>
<remarks>Non-Employee Stock Options - Direct Ownership
Exercise price $2.05, expiration 5-3-2001, Common Stock, 5,000 Options
Exercise price $1.35, expiration 3-17-2012, Common Stock, 5,000 Options
Exercise price $1.195, expiration 3-3-2013, Common Stock, 5,000 Options</remarks>
<ownerSignature>
<signatureName>A. John Knapp</signatureName>
<signatureDate>2003-12-22</signatureDate>
</ownerSignature>
</ownershipDocument>

