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

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2005-05-03</periodOfReport>

    <issuer>
        <issuerCik>0000052617</issuerCik>
        <issuerName>IRWIN FINANCIAL CORP</issuerName>
        <issuerTradingSymbol>IFC</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001160683</rptOwnerCik>
            <rptOwnerName>KIME BRADLEY J</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>IRWIN FINANCIAL CORPORATION</rptOwnerStreet1>
            <rptOwnerStreet2>500 WASHINGTON STREET</rptOwnerStreet2>
            <rptOwnerCity>COLUMBUS</rptOwnerCity>
            <rptOwnerState>IN</rptOwnerState>
            <rptOwnerZipCode>47201</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>President of Subsidiary</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>COMMON STOCK</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2140</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>NON-QUALIFIED STOCK OPTION (RIGHT TO BUY)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>20.47</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2005-05-03</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>7000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <value>2015-05-02</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>COMMON STOCK</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>7000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>7000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Includes 6 additional shares acquired on 3/25/2005 through participation in the Irwin Financial Corporation Dividend Reinvestment and Common Stock Purchase Plan.  The Plan provides for the purchase of fractional shares.  The number reported is the nearest whole number of shares.</footnote>
        <footnote id="F2">Between 1/1/05 and 4/21/05, the reporting person acquired 43 shares of Irwin Financial Corporation common stock under the Irwin Financial Corporation Employees' Stock Purchase Plan III (Plan) including shares acquired pursuant to a dividend reinvestment feature of the Plan.  The Plan provides for the purchase of fractional shares.  The number reported is the nearest whole number.</footnote>
        <footnote id="F3">The Plan provides for phased-in vesting of rights to exercise granted stock options.  In the year of the grant, optionee may exercise 25% of total options granted.  In each of the three years immediately following the year of the grant, optionee may exercise an additional 25% of the options granted.  Grant of option was made to reporting person in transaction exempt under Rule 16b-3.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>By:  /s/ Ellen Z. Mufson, Attorney-in-Fact for Bradley J. Kime</signatureName>
        <signatureDate>2005-05-05</signatureDate>
    </ownerSignature>
</ownershipDocument>
