Document and Entity Information (USD $)
12 Months Ended
Jun. 30, 2015
Aug. 14, 2015
Dec. 31, 2014
Document And Entity Information [Abstract]      
Document Type 10-K    
Amendment Flag false    
Document Period End Date Jun. 30, 2015    
Document Fiscal Year Focus 2015    
Document Fiscal Period Focus FY    
Trading Symbol QNST    
Entity Registrant Name QUINSTREET, INC    
Entity Central Index Key 0001117297    
Current Fiscal Year End Date --06-30    
Entity Well-known Seasoned Issuer No    
Entity Current Reporting Status Yes    
Entity Voluntary Filers No    
Entity Filer Category Accelerated Filer    
Entity Common Stock, Shares Outstanding   45,004,701  
Entity Public Float     $ 215,190,902