Document And Entity Information - USD ($)
$ in Millions
12 Months Ended
Sep. 30, 2018
Dec. 14, 2018
Mar. 30, 2018
Document And Entity Information [Abstract]      
Entity Registrant Name Outlook Therapeutics, Inc.    
Entity Central Index Key 0001649989    
Trading Symbol ons    
Entity Current Reporting Status Yes    
Entity Voluntary Filers No    
Current Fiscal Year End Date --09-30    
Entity Filer Category Non-accelerated Filer    
Entity Well-known Seasoned Issuer No    
Entity Common Stock, Shares Outstanding   85,091,062  
Entity Public Float     $ 15.6
Document Type 10-K    
Document Period End Date Sep. 30, 2018    
Amendment Flag false    
Document Fiscal Year Focus 2018    
Document Fiscal Period Focus FY    
Entity Shell Company false    
Entity Small Business true    
Entity Emerging Growth Company true    
Entity Ex Transition Period true