Objective: Hyperbaric oxygen therapy (HBOT) involves breathing pure oxygen in a high-pressure chamber. HBOT is a wellestablished treatment for several diseases, such as serious infections, chronic diabetic foot ulcer, radiation injury, and hidradenitis suppurativa. There are various troublesome diseases that decrease pleasure in life in patients. HBOT has excellent effects in improving QOL in patients with acute and chronic diseases. The present study aimed at assessing the researches that focus on improving the QOL after HBO treatments. Methods:A systematic quest was conducted to evaluate English papers (clinical trials) that were published before April 2017. We searched PubMed, institute of scientific information (ISI), SCOPUS, Web of Science, Ovid, Science direct, ProQuest, Wiley, Cochran, Ebsco host, and Google Scholar. The reference lists of all the articles and electronic journals were searched for further studies. The JAMA users guide evaluation scales for RCTs was used to assess quality of the researched articles. Inclusion and exclusion criteria were extracted according to the scientific criteria. Sample size was 806 patients.Results: Finally, 15 published articles were extracted. Most researches were done in UK (26.7%), Israel (20%), and Sweden (20%). The mean age in HBOT group was 41.88, with a male to female ratio of 1.52. The mean age in the control group was 38.29, with a male to female ratio of 2.14. The most frequent clinical trials were those on the treatment of diabetic foot ulcer (20%), post-concussion syndrome (13.3%), pelvic radiotherapy (13.3%), and chronic arm lymphedema after radiotherapy (13.3%). The most QOL questionnaires used were SF-36 (21.4%), EORTC (European organization for research and treatment of cancer) QLQ-C30, head and neck cancer module (H&N35), and performance status scale (PSS).Conclusions: A significant effect of HBOT on improving QOL in patients' outcomes and symptoms was found compared with the control group. We found improved QOL in patients with diabetic foot ulcer, post-concussion syndrome, pelvic radiotherapy, post stroke, hidradenitis suppurativa, tonsillar fossa tumor radiotherapy, jaw osteonecrosis, and fibromyalgia syndrome. We suggest that HBOT be added to conventional treatment of these patients as an adjuvant.