Tehran University of Medical Sciences Iranian Journal of Psychiatry 1735-4587 18 2 2023 03 15 248 257 Zahra Beygi Faculty of Humanities, Department of Clinical Psychology, Islamic Azad University of Sirjan, Sirjan, Iran. Reyhane Tighband Jangali Faculty of Humanities, Department of Clinical Psychology, Anar Islamic Azad University, Kerman, Iran. Nafiseh Derakhshan Department of Psychology and Educational Sciences, University of Allameh Tabatabaei, Tehran, Iran. Mina Alidadi Department of Clinical Psychology, Bam University of Medical Sciences, Bam, Iran. Farzane Javanbakhsh Faculty of Humanities, Department of Clinical Psychology, Islamic Azad University of Sirjan, Sirjan, Iran. Mahdieh Mahboobizadeh Faculty of Humanities, Department of Clinical Psychology, Islamic Azad University of Sirjan, Sirjan, Iran. 2022 11 29 2022 12 19 Objective: Emotional disturbances are the most common mental health problems in different populations and societies. We intend to provide the latest evidence related to the effectiveness of Acceptance and Commitment Therapy (ACT) on depression and anxiety by reviewing systematic review and meta-analysis studies published in the last three years. Method: PubMed and Google Scholar databases were systematically searched between January 1, 2019 and November 25, 2022 with relevant keywords for English systematic review and meta-analysis articles reviewing the utilization of ACT to reduce anxiety and depression symptoms. Results: 25 articles were included in our study: 14 systematic review and meta-analysis studies and 11 systematic reviews. These studies have investigated the effects of ACT on depression and anxiety in populations of children or adults, mental health patients, patients with different cancers or multiple sclerosis, people with audiological problems, parents or caregivers of children with mental or physical illnesses as well as normal people. Furthermore, they have examined the effects of ACT in individual, group, Internet, computerized, or combined delivery formats. Most of the reviewed studies reported significant effect sizes (small to large effect sizes) of ACT, regardless of the delivery method, compared to passive (placebo, waitlist) and active (treatment as usual and other psychological interventions except cognitive behavioral therapy (CBT)) controls for depression and anxiety. Conclusion: Recent literature mainly agrees on the small to moderate effect sizes of ACT on depression and anxiety symptoms in different populations. https://ijps.tums.ac.ir/index.php/ijps/article/view/3444 https://ijps.tums.ac.ir/index.php/ijps/article/download/3444/1108