v3.8.0.1
Document And Entity Information - shares
6 Months Ended
Mar. 31, 2018
May 14, 2018
Document And Entity Information [Abstract]    
Entity Registrant Name Oncobiologics, Inc.  
Entity Central Index Key 0001649989  
Trading Symbol ons  
Current Fiscal Year End Date --09-30  
Entity Filer Category Smaller Reporting Company  
Entity Common Stock, Shares Outstanding   32,332,568
Document Type 10-Q  
Document Period End Date Mar. 31, 2018  
Amendment Flag false  
Document Fiscal Year Focus 2018  
Document Fiscal Period Focus Q2