<SEC-DOCUMENT>0001127602-24-025995.txt : 20241025
<SEC-HEADER>0001127602-24-025995.hdr.sgml : 20241025
<ACCEPTANCE-DATETIME>20241025162433
ACCESSION NUMBER:		0001127602-24-025995
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20241023
FILED AS OF DATE:		20241025
DATE AS OF CHANGE:		20241025

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Plunkett Debora A
		CENTRAL INDEX KEY:			0001699997
		ORGANIZATION NAME:           	

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-41194
		FILM NUMBER:		241397357

	MAIL ADDRESS:	
		STREET 1:		6501 LEGACY DRIVE
		CITY:			PLANO
		STATE:			TX
		ZIP:			75024

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			MERCURY SYSTEMS INC
		CENTRAL INDEX KEY:			0001049521
		STANDARD INDUSTRIAL CLASSIFICATION:	ELECTRONIC COMPONENTS & ACCESSORIES [3670]
		ORGANIZATION NAME:           	04 Manufacturing
		IRS NUMBER:				042741391
		STATE OF INCORPORATION:			MA
		FISCAL YEAR END:			0630

	BUSINESS ADDRESS:	
		STREET 1:		50 MINUTEMAN ROAD
		CITY:			ANDOVER
		STATE:			MA
		ZIP:			01810
		BUSINESS PHONE:		9782561300

	MAIL ADDRESS:	
		STREET 1:		50 MINUTEMAN ROAD
		CITY:			ANDOVER
		STATE:			MA
		ZIP:			01810

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	MERCURY COMPUTER SYSTEMS INC
		DATE OF NAME CHANGE:	19971112
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>form4.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2024-10-23</periodOfReport>

    <issuer>
        <issuerCik>0001049521</issuerCik>
        <issuerName>MERCURY SYSTEMS INC</issuerName>
        <issuerTradingSymbol>MRCY</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001699997</rptOwnerCik>
            <rptOwnerName>Plunkett Debora A</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>50 MINUTEMAN ROAD</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>ANDOVER</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>01810</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>0</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2024-10-23</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>4832</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>16171</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Represents deferred stock units (DSUs) that vest on the earlier of the first anniversary of the grant date and the next annual meeting of shareholders. Vested DSUs do not convert into shares of common stock until the date on which the reporting person ceases to be a member of our Board of Directors.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Douglas Munro, attorney-in-fact</signatureName>
        <signatureDate>2024-10-25</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
