-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
Originator-Key-Asymmetric:
 MFgwCgYEVQgBAQICAf8DSgAwRwJAW2sNKK9AVtBzYZmr6aGjlWyK3XmZv3dTINen
 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 NoIKw/LcIxT2bDq1rhb+/yPm+UWY6JsmtFTItthfWh4gXqH7ndWXbWUXNdEyKmjh
 kku0v/gc71XSx+kWaO0ttg==

<SEC-DOCUMENT>0000713671-10-000017.txt : 20100409
<SEC-HEADER>0000713671-10-000017.hdr.sgml : 20100409
<ACCEPTANCE-DATETIME>20100409113017
ACCESSION NUMBER:		0000713671-10-000017
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20100409
FILED AS OF DATE:		20100409
DATE AS OF CHANGE:		20100409

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			HIEB WILLIAM J
		CENTRAL INDEX KEY:			0001252518

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-34242
		FILM NUMBER:		10741497

	MAIL ADDRESS:	
		STREET 1:		4 BRANDYWINE AVE
		CITY:			DOWNINGTOWN
		STATE:			PA
		ZIP:			19335

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			DNB FINANCIAL CORP /PA/
		CENTRAL INDEX KEY:			0000713671
		STANDARD INDUSTRIAL CLASSIFICATION:	NATIONAL COMMERCIAL BANKS [6021]
		IRS NUMBER:				232222567
		STATE OF INCORPORATION:			PA
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		4 BRANDYWINE AVE
		CITY:			DOWNINGTOWN
		STATE:			PA
		ZIP:			19335
		BUSINESS PHONE:		6102691040

	MAIL ADDRESS:	
		STREET 1:		4 BRANDYWINE AVENUE
		CITY:			DOWNINGTOWN
		STATE:			PA
		ZIP:			19335
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2010-04-09</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000713671</issuerCik>
        <issuerName>DNB FINANCIAL CORP /PA/</issuerName>
        <issuerTradingSymbol>DNFB</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001252518</rptOwnerCik>
            <rptOwnerName>HIEB WILLIAM J</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>4 BRANDYWINE AVE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>DOWNINGTOWN</rptOwnerCity>
            <rptOwnerState>PA</rptOwnerState>
            <rptOwnerZipCode>19335</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>President &amp; COO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>DNBF Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2010-04-09</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>419</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>5.91</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>18808</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>DNBF Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2010-04-09</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>8</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>5.91</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>18816</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">1684 shares owned jointly with spouse</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Gerald F Sopp for William J Hieb</signatureName>
        <signatureDate>2010-04-09</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
-----END PRIVACY-ENHANCED MESSAGE-----