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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2015-07-14</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000722830</issuerCik>
        <issuerName>IMMUNOMEDICS INC</issuerName>
        <issuerTradingSymbol>IMMU</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001202016</rptOwnerCik>
            <rptOwnerName>GOLDENBERG CYNTHIA L</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O IMMUNOMEDICS, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>300 AMERICAN ROAD</rptOwnerStreet2>
            <rptOwnerCity>MORRIS PLAINS</rptOwnerCity>
            <rptOwnerState>NJ</rptOwnerState>
            <rptOwnerZipCode>07950</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>President and CEO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Performance Rights</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F1"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2015-07-14</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>1500000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0.00</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2020-07-14</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock, par value $0.01 per share</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>1500000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1500000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnote</value>
                    <footnoteId id="F2"/>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Each performance right represents a contingent right to receive one share of Immunomedics, Inc. common stock.  The performance rights will vest  (i) as to 500,000 shares (a) on or after the third anniversary of the grant date and (b) upon Immunomedics, Inc. common stock achieving a fair market value of $7.35 or higher based on the average closing price for the prior 30 consecutive trading days;  (ii) as to 500,000 shares (a) on or after the third anniversary of the grant date and (b) upon Immunomedics, Inc. common stock achieving a fair market value of $11.00 or higher based on the average closing price for the prior 30 consecutive trading days; and (iii) as to 500,000 shares (a) on or after the third anniversary of the grant date and (b) upon Immunomedics, Inc. common stock achieving a fair market value of $15.00 or higher based on the average closing price for  the prior 30 consecutive trading days.</footnote>
        <footnote id="F2">The reporting person's spouse was granted these performance rights under the Issuer's 2014 Long-Term Incentive Plan.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Cynthia L. Goldenberg</signatureName>
        <signatureDate>2015-07-16</signatureDate>
    </ownerSignature>
</ownershipDocument>
