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

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2009-07-17</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000949961</issuerCik>
        <issuerName>INCOME OPPORTUNITY REALTY INVESTORS INC /TX/</issuerName>
        <issuerTradingSymbol>IOT</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0000733590</rptOwnerCik>
            <rptOwnerName>TRANSCONTINENTAL REALTY INVESTORS INC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>1800 VALLEY VIEW LANE</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 300</rptOwnerStreet2>
            <rptOwnerCity>DALLAS</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>75234</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>common stock, par value $0,01 per share</value>
            </securityTitle>
            <transactionDate>
                <value>2009-07-17</value>
            </transactionDate>
            <deemedExecutionDate>
                <value>2009-07-20</value>
            </deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>2518934</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>6.21</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>3556118</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <ownerSignature>
        <signatureName>Transcontinental Realty Investors, Inc</signatureName>
        <signatureDate>2009-07-21</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>By: Gene S. Bertcher, EVP</signatureName>
        <signatureDate>2009-07-21</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0303
4
2009-07-17
0
0000949961
INCOME OPPORTUNITY REALTY INVESTORS INC /TX/
IOT
0000733590
TRANSCONTINENTAL REALTY INVESTORS INC
1800 VALLEY VIEW LANE
SUITE 300
DALLAS
TX
75234
0
0
1
0
common stock, par value $0,01 per share
2009-07-17
2009-07-20
4
P
0
2518934
6.21
A
3556118
D
Transcontinental Realty Investors, Inc
2009-07-21
By: Gene S. Bertcher, EVP
2009-07-21