There is a controversy about the efficacy of hyperbaric oxygen (HBO) therapy for the treatment of autism. This study systematically reviews the current evidences for treating of autism with HBO therapy. According to PRISMA guidelines for a systematic review, the databases of MEDLINE/Pubmed, Google Scholar, and Randomised Controlled Trials in Hyperbaric Medicine were electronically searched. In addition, medical subject heading terms and text words for hyperbaric oxygen therapy and autism were used. The main inclusion criteria were published studies which reported the original data from the trials conducted on the patients with autism and assessed outcomes with a valid and reliable instrument. A quality assessment was also conducted. The electronically search resulted in 18 title of publications. Two studies were randomized, double-blind, controlled-clinical trials. While some uncontrolled and controlled studies suggested that HBO therapy is effective for the treatment of autism, these promising effects are not replicated. Therefore, sham-controlled studies with rigorous methodology are required to be conducted in order to provide scientific evidence-based HBO therapy for autism treatment.