Background: Acceptance and commitment therapy (ACT), a third-generation cognitive behavioral therapy (CBT), has proved its efficacy amidst various mental disorders. A growing body of studies has shown that ACT can improve obsessive-compulsive disorder (OCD) severity in recent years. To assess the effect of ACT on OCD, we carried out a systematic review and meta-analysis to provide a basis for therapists to use different psychological dimensions of ACT for OCD. Methods: PubMed, the Cochrane Library, EMBASE, EBSCO Host, and literature references were searched until May 2021. Randomized controlled trials (RCTs) and other study designs assessing the effect of ACT among adults suffering from OCD were examined. Results: Fourteen studies, including 413 participants, published between 2010 and 2021 were identified. ACT made statistically significant progress in the Yale–Brown Obsessive–Compulsive Scale (YBOCS) compared with control conditions. Conclusion: After reviewing all the ACT studies, we acknowledge the plausibility of ACT in treating OCD and improving its symptoms for the clinical population. ACT can also be an adjunct therapy for other well-established treatments. It also favors targeting psychological inflexibility. Further well-controlled and high-quality RCTs are required for a better conclusion in further studies. Keywords: obsessive–compulsive disorder, acceptance and commitment therapy, psychological inflexibility, meta-analysis, systematic review