<SEC-DOCUMENT>0000909108-15-000036.txt : 20150402
<SEC-HEADER>0000909108-15-000036.hdr.sgml : 20150402
<ACCEPTANCE-DATETIME>20150402161717
ACCESSION NUMBER:		0000909108-15-000036
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20150401
FILED AS OF DATE:		20150402
DATE AS OF CHANGE:		20150402

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			DIAMOND HILL INVESTMENT GROUP INC
		CENTRAL INDEX KEY:			0000909108
		STANDARD INDUSTRIAL CLASSIFICATION:	INVESTMENT ADVICE [6282]
		IRS NUMBER:				650190407
		STATE OF INCORPORATION:			OH
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		325 JOHN H MCCONNELL BLVD
		STREET 2:		SUITE 200
		CITY:			COLUMBUS
		STATE:			OH
		ZIP:			43215
		BUSINESS PHONE:		6142553333

	MAIL ADDRESS:	
		STREET 1:		325 JOHN H MCCONNELL BLVD
		STREET 2:		SUITE 200
		CITY:			COLUMBUS
		STATE:			OH
		ZIP:			43215

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	BANC STOCK GROUP INC
		DATE OF NAME CHANGE:	19971016

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	HEARTLAND GROUP OF COMPANIES INC
		DATE OF NAME CHANGE:	19940301

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	HEARTLAND FINANCIAL GROUP INC
		DATE OF NAME CHANGE:	19930714

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Line Thomas Edward
		CENTRAL INDEX KEY:			0001629546

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-24498
		FILM NUMBER:		15747857

	MAIL ADDRESS:	
		STREET 1:		325 JOHN H. MCCONNELL BLVD., SUITE 200
		CITY:			COLUMBUS
		STATE:			OH
		ZIP:			43215
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>wf-form4_142800582718657.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2015-04-01</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000909108</issuerCik>
        <issuerName>DIAMOND HILL INVESTMENT GROUP INC</issuerName>
        <issuerTradingSymbol>DHIL</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001629546</rptOwnerCik>
            <rptOwnerName>Line Thomas Edward</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>325 JOHN H. MCCONNELL BLVD.,</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 200</rptOwnerStreet2>
            <rptOwnerCity>COLUMBUS</rptOwnerCity>
            <rptOwnerState>OH</rptOwnerState>
            <rptOwnerZipCode>43215</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Chief Financial Officer</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common</value>
            </securityTitle>
            <transactionDate>
                <value>2015-04-01</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>2000</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>3763</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>184</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By 401k</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Restricted Stock Unit</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F2"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2015-04-01</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>C</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>3000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F2"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>3000.0</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>12000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Reflects vesting of 3,000 restricted stock units.  Units totaling 1,000 withheld for payment of taxes, leaving 2,000 units that converted to common shares.</footnote>
        <footnote id="F2">Remaining Restricted Stock Units (&quot;RSUs&quot;) under this award are convertible into shares of common stock with 3,000 units vesting upon the completion of each of the 4 years ending April 1, 2016 through April 1, 2019, subject to the requirement of continuous service through the applicable vesting dates. After vesting, each RSU is then further restricted from sale for a five year period.  RSUs under this award represent a contingent right to receive once share of Common Stock.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Gary Young by POA</signatureName>
        <signatureDate>2015-04-02</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
