<SEC-DOCUMENT>0001104659-12-017558.txt : 20120312
<SEC-HEADER>0001104659-12-017558.hdr.sgml : 20120310
<ACCEPTANCE-DATETIME>20120312163617
ACCESSION NUMBER:		0001104659-12-017558
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20120312
FILED AS OF DATE:		20120312
DATE AS OF CHANGE:		20120312

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Stone James
		CENTRAL INDEX KEY:			0001515176

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	814-00832
		FILM NUMBER:		12684386

	MAIL ADDRESS:	
		STREET 1:		C/O NEW MOUNTAIN FINANCE CORPORATION
		STREET 2:		787 7TH AVENUE, 48TH FLOOR
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10019

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			New Mountain Finance Corp
		CENTRAL INDEX KEY:			0001496099
		IRS NUMBER:				272978010
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		787 SEVENTH AVENUE, 48TH FLOOR
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10019
		BUSINESS PHONE:		(212) 720-0300

	MAIL ADDRESS:	
		STREET 1:		787 SEVENTH AVENUE, 48TH FLOOR
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10019

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	New Mountain Guardian Corp
		DATE OF NAME CHANGE:	20100706
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>a4.xml
<DESCRIPTION>4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0304</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2012-03-12</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001496099</issuerCik>
        <issuerName>New Mountain Finance Corp</issuerName>
        <issuerTradingSymbol>NMFC</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001515176</rptOwnerCik>
            <rptOwnerName>Stone James</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O NEW MOUNTAIN CAPITAL, L.L.C.</rptOwnerStreet1>
            <rptOwnerStreet2>787 7TH AVENUE, 48TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10019</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Section 16 Officer</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2012-03-12</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>11250</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>13.51</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>30180.22</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">The price reported is the average weighted price.  The shares were purchased in multiple transactions at prices ranging from $13.449 to $13.5414, inclusive.  The reporting person undertakes to provide to the SEC, the issuer and any security holder, upon request, full information regarding the number of shares and the prices at which the shares were purchased.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ James Stone</signatureName>
        <signatureDate>2012-03-12</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
