Document And Entity Information - shares	9 Months Ended
	May. 30, 2015	Jul. 03, 2015
Document Information [Line Items]
Entity Registrant Name	UNIFIRST CORP
Trading Symbol	unf
Document Type	10-Q
Current Fiscal Year End Date	--08-29
Amendment Flag	false
Entity Central Index Key	0000717954
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Well-known Seasoned Issuer	Yes
Document Period End Date	May 30, 2015
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q3
Common Class B [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		4,854,519
Common Class A [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		15,245,588