Document and Entity Information - shares	3 Months Ended
	Sep. 27, 2019	Oct. 31, 2019
Document Documentand Entity Information [Abstract]
Title of 12(g) Security	Common Stock, par value $0.01 per share
Entity Incorporation, State or Country Code	MA
Document Transition Report	false
Document Quarterly Report	true
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 27, 2019
Entity File Number	0-23599
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Trading Symbol	MRCY
Entity Registrant Name	MERCURY SYSTEMS, INC.
City Area Code	978
Local Phone Number	256-1300
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Shell Company	false
Entity Central Index Key	0001049521
Current Fiscal Year End Date	--07-03
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		55,536,945
Entity Tax Identification Number	04-2741391
Entity Address, Address Line One	50 MINUTEMAN ROAD
Entity Address, Postal Zip Code	01810
Entity Address, City or Town	ANDOVER
Entity Address, State or Province	MA
Entity Small Business	false
Entity Emerging Growth Company	false
Security Exchange Name	NASDAQ