-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
Originator-Key-Asymmetric:
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 CHPbCbMIu0TnTkQWqq/ojY/f0rZ6BAcGrbQzUCZ7/vmIW8LoUJdJbaTAVRQtxbib
 ko+aAPb1qf9YvJu1yf736w==

<SEC-DOCUMENT>0001477548-09-000001.txt : 20091209
<SEC-HEADER>0001477548-09-000001.hdr.sgml : 20091209
<ACCEPTANCE-DATETIME>20091209171525
ACCESSION NUMBER:		0001477548-09-000001
CONFORMED SUBMISSION TYPE:	D
PUBLIC DOCUMENT COUNT:		1
ITEM INFORMATION:		Rule 506
FILED AS OF DATE:		20091209
DATE AS OF CHANGE:		20091209
EFFECTIVENESS DATE:		20091209

FILER:

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			Mariner IO Mortgage Fund, L.P.
		CENTRAL INDEX KEY:			0001477548
		IRS NUMBER:				271231404
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		D
		SEC ACT:		1933 Act
		SEC FILE NUMBER:	021-136792
		FILM NUMBER:		091231548

	BUSINESS ADDRESS:	
		STREET 1:		500 MAMARONECK AVENUE
		STREET 2:		4TH FLOOR
		CITY:			HARRISON
		STATE:			NY
		ZIP:			10528
		BUSINESS PHONE:		914-670-4300

	MAIL ADDRESS:	
		STREET 1:		500 MAMARONECK AVENUE
		STREET 2:		4TH FLOOR
		CITY:			HARRISON
		STATE:			NY
		ZIP:			10528
</SEC-HEADER>
<DOCUMENT>
<TYPE>D
<SEQUENCE>1
<FILENAME>primary_doc.xml
<TEXT>
<XML>
<?xml version="1.0"?>
<edgarSubmission>

    <schemaVersion>X0603</schemaVersion>

    <submissionType>D</submissionType>

    <testOrLive>LIVE</testOrLive>

    <primaryIssuer>
        <cik>0001477548</cik>
        <entityName>Mariner IO Mortgage Fund, L.P.</entityName>
        <issuerAddress>
            <street1>500 MAMARONECK AVENUE</street1>
            <street2>4TH FLOOR</street2>
            <city>HARRISON</city>
            <stateOrCountry>NY</stateOrCountry>
            <zipCode>10528</zipCode>
        </issuerAddress>
        <issuerPhoneNumber>914-670-4300</issuerPhoneNumber>
        <jurisdictionOfInc>DELAWARE</jurisdictionOfInc>
        <issuerPreviousNameList>
            <value>None</value>
        </issuerPreviousNameList>
        <edgarPreviousNameList>
            <value>None</value>
        </edgarPreviousNameList>
        <entityType>Limited Partnership</entityType>
        <yearOfInc>
            <withinFiveYears>true</withinFiveYears>
            <value>2009</value>
        </yearOfInc>
    </primaryIssuer>

    <relatedPersonsList>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>William</firstName>
                <middleName>J.</middleName>
                <lastName>Michaelcheck</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>500 Mamaroneck Avenue</street1>
                <street2>4th Floor</street2>
                <city>Harrison</city>
                <stateOrCountry>NY</stateOrCountry>
                <zipCode>10528</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Executive Officer</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification>Executive Officer of Mariner, Inc., sole General Partner of Mariner GP, L.P., the General Partner of the Issuer.</relationshipClarification>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>Bracebridge</firstName>
                <middleName>H.</middleName>
                <lastName>Young, Jr.</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>500 Mamaroneck Avenue</street1>
                <street2>4th Floor</street2>
                <city>Harrison</city>
                <stateOrCountry>NY</stateOrCountry>
                <zipCode>10528</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Executive Officer</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification>Executive Officer of Mariner, Inc., sole General Partner of Mariner GP, L.P., the General Partner of the Issuer.</relationshipClarification>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>Charles</firstName>
                <middleName>R.</middleName>
                <lastName>Howe II</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>500 Mamaroneck Avenue</street1>
                <street2>4th Floor</street2>
                <city>Harrison</city>
                <stateOrCountry>NY</stateOrCountry>
                <zipCode>10528</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Executive Officer</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification>Executive Officer of Mariner, Inc., sole General Partner of Mariner GP, L.P., the General Partner of the Issuer.</relationshipClarification>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>Peter</firstName>
                <middleName>J.</middleName>
                <lastName>O'Rourke</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>500 Mamaroneck Avenue</street1>
                <street2>4th Floor</street2>
                <city>Harrison</city>
                <stateOrCountry>NY</stateOrCountry>
                <zipCode>10528</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Executive Officer</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification>Executive Officer of Mariner, Inc., sole General Partner of Mariner GP, L.P., the General Partner of the Issuer.</relationshipClarification>
        </relatedPersonInfo>
    </relatedPersonsList>

    <offeringData>
        <industryGroup>
            <industryGroupType>Pooled Investment Fund</industryGroupType>
            <investmentFundInfo>
                <investmentFundType>Hedge Fund</investmentFundType>
                <is40Act>false</is40Act>
            </investmentFundInfo>
        </industryGroup>
        <issuerSize>
            <aggregateNetAssetValueRange>Decline to Disclose</aggregateNetAssetValueRange>
        </issuerSize>
        <federalExemptionsExclusions>
            <item>06</item>
        </federalExemptionsExclusions>
        <typeOfFiling>
            <newOrAmendment>
                <isAmendment>false</isAmendment>
            </newOrAmendment>
            <dateOfFirstSale>
                <yetToOccur>true</yetToOccur>
            </dateOfFirstSale>
        </typeOfFiling>
        <durationOfOffering>
            <moreThanOneYear>true</moreThanOneYear>
        </durationOfOffering>
        <typesOfSecuritiesOffered>
            <isEquityType>true</isEquityType>
            <isPooledInvestmentFundType>true</isPooledInvestmentFundType>
        </typesOfSecuritiesOffered>
        <businessCombinationTransaction>
            <isBusinessCombinationTransaction>false</isBusinessCombinationTransaction>
            <clarificationOfResponse></clarificationOfResponse>
        </businessCombinationTransaction>
        <minimumInvestmentAccepted>10000</minimumInvestmentAccepted>
        <salesCompensationList></salesCompensationList>
        <offeringSalesAmounts>
            <totalOfferingAmount>Indefinite</totalOfferingAmount>
            <totalAmountSold>0</totalAmountSold>
            <totalRemaining>Indefinite</totalRemaining>
            <clarificationOfResponse></clarificationOfResponse>
        </offeringSalesAmounts>
        <investors>
            <hasNonAccreditedInvestors>false</hasNonAccreditedInvestors>
            <totalNumberAlreadyInvested>0</totalNumberAlreadyInvested>
        </investors>
        <salesCommissionsFindersFees>
            <salesCommissions>
                <dollarAmount>0</dollarAmount>
            </salesCommissions>
            <findersFees>
                <dollarAmount>0</dollarAmount>
            </findersFees>
            <clarificationOfResponse></clarificationOfResponse>
        </salesCommissionsFindersFees>
        <useOfProceeds>
            <grossProceedsUsed>
                <dollarAmount>0</dollarAmount>
            </grossProceedsUsed>
            <clarificationOfResponse></clarificationOfResponse>
        </useOfProceeds>
        <signatureBlock>
            <authorizedRepresentative>false</authorizedRepresentative>
            <signature>
                <issuerName>Mariner IO Mortgage Fund, L.P.</issuerName>
                <signatureName>/s/ Charles R. Howe II</signatureName>
                <nameOfSigner>Charles R. Howe II</nameOfSigner>
                <signatureTitle>Executive Officer of the GP of the GP of the Issuer</signatureTitle>
                <signatureDate>2009-12-09</signatureDate>
            </signature>
        </signatureBlock>
    </offeringData>
</edgarSubmission>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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