Background: The aim of the present study was to compare effectiveness of metacognitive therapy (MCT) and acceptance commitment therapy (ACT) on reducing syndromes, psychological capital and quality of life of patients suffering from irritable bowel syndrome (IBS). Materials and methods: Research method was quasi-experimental with pre-test, post-test, three-month follow-up and control group. Statistical population was all 20-40 years old females suffering from IBS who applied to Counseling Center of Pharmaceutical Sciences University located in Tehran City. Through available sampling, 45 patients were selected and assigned randomly in experimental group 1 (MCT), experimental group 2 (ACT) and control group (15 in each group). The Psychological Capital Inventory (Luthans, 1992) and Quality of Life Inventory (Ware & Sherbourne, 1992) were administered pre-test, posttest and follow-up period. The therapeutic packages of acceptance, commitment therapy and metacognitive therapy applied on experimental groups for eight 90-minute sessions once a week. Control group was placed in a waiting list. Results: Both therapeutic methods equally increased psychological capital and quality of life in patients suffering from IBS. According to physicians’ report and own patients themselves, the symptoms of the disease were significantly reduced. Three-month follow-up confirmed these results. Conclusion: Since psychosocial factors, in addition to biological elements, influence on severity of IBS symptoms, improving healthy quality of life and psychological capital indicators should be paid attention to prevent and treat this disorder.