Background: Intercessory prayer (intercession) is an ancient intervention applied with the aim of easing morbidity and health improvement. It is practiced by many faiths and involves a person or group setting time aside to petition God on behalf of another who is in some kind of need. Objectives: This systematic review is aimed to overview curative and clinical effect of Prayer on different diseases. Methods: This review article was carried out by searching studies in PubMed, Medline, Web of Science, and IranMedex databases. The initial search strategy identified about 123 references. In this study, 65 studies was accepted for further screening and met all our inclusion criteria (in English, full text, and dated mainly from the year 1992 to 2016). The search terms were “Complementary and Alternative Therapies, prayer, Intercessory prayer, curative Effect”. Result: the result of this systematic review show the curative samples of intercessory prayer, with one study in each of different categories of outcome. We provide a critical analysis of the clinical aspect of such a research rather than its philosophical dimensions. The findings of this study include only the cases of positive effect of Prayer on human as well as nonhuman species. instead, It was shown that prayer has clinical effect in many diseases including Infertility, Wound healing, cardiovascular disease, Rheumatoid arthritis, Bloodstream infection, Depression and anxiety, Cystic fibrosis, Kidney dialysis, General anesthesia, Alcohol abuse, Psychiatric conditions, Impaired auditory, hearing and/or vision, Cancer, Spinal surgery, HIV, WART, Pregnancy, Pulmonary diseases, Chronic diseases. In addition, Intercession also showed decrease length of hospital stay and duration of fever in septic patients, increase immune function. Conclusions: In this study, curative and clinical Effect of intercession on different diseases were presented using published articles in scientific sites. Besides, the concept of intercessory prayer, different forms of prayer, literature concerning efficacy of clinical trials and non-clinical trials were reviewed. It was concluded that the potential power of faith in healing of many diseases was observed. Although some reviews or meta-analysis stated null or small therapeutic effect, further clinical un-biased studies are still required to deny or confirm its effectiveness
