Introduction: Schizophrenia and psychotic disorders are chronic conditions. Although antipsychotic medicationsare the first line of treatment, many patients continued to have symptoms. Acceptance and Commitment Therapy(ACT) is a therapy that applies mindfulness to teach patients accepting the existence of symptoms rather than avoidthem. A meta-analysis was conducted to measure the efficacy of ACT in treatment of psychosis.Methods: A systematic review search was conducted using the following keywords: "acceptance andcommitment therapy", "randomized", "clinical trials", "psychosis"," schizophrenia", and "major depressive disorderAND psychosis". All studies were read by two authors and checked for eligibility. Studies were included if randomlyallocate to ACT or usual treatment (TAU), and psychosis as diagnosis. Mantel and Haenszel approach was used todetermine the heterogeneity in the study. For quantitative outcomes, standardized mean difference between ACTand TAU was used to summarize effect size, while relative risk was used for categorical outcomes along with 95%confidence interval.Results: 217 studies were identified. 92 studies were selected for review after removing the duplications. Atotal of 4 studies were included in quantitative-synthesis. The mean age for the participants was 38 years of age.Regarding treatment outcomes, there was a significant difference between the two arms in the degree of change ofnegative symptoms (p=0.008), but the difference was not significant for positive symptoms. There was a reduction ofre-hospitalization rate at 4 months in ACT compared to TAU in participants with psychosis.Conclusions: ACT is a promising adjunctive therapy for patient with psychosis.