Document And Entity Information	9 Months Ended
	May 25, 2013	Jun. 27, 2013 Common Class A [Member]	Jun. 27, 2013 Common Class B [Member]
Document Information [Line Items]
Entity Registrant Name	UNIFIRST CORP
Document Type	10-Q
Current Fiscal Year End Date	--08-31
Entity Common Stock, Shares Outstanding		15,122,075	4,873,277
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 25, 2013
Document Fiscal Year Focus	2013
Document Fiscal Period Focus	Q3