The current study included randomized controlled trials (RCTs) to assess the benefits of Acceptance and commitment therapy (ACT) for chronic pain. Searches were conducted in Web of Science, PsycINFO, PubMed, Scopus, Cochrane Library, and Embase from inception until September 30, 2022. Thirty-three RCTs, including 2293 participants, were included. Small to medium effect sizes for pain intensity/physical function favoring ACT were found both at post-treatment (pain intensity: g = 0.44; physical function: g = 0.59) and follow-up (pain intensity: g = 0.34; physical function: g = 0.56). The effect sizes on psychological outcomes were significant at post-treatment (depression: g = 0.43; anxiety: g = 0.43; quality of life: g = 0.45) and follow-up (depression: g = 0.43; anxiety: g = 0.35; quality of life: g = 0.43). The results of the trial sequential analyses indicated that pooled estimates were unlikely to be incidental findings, as effects of multiple testing were controlled and power was adequate. Face-to-face ACT yielded significantly larger effects on physical outcomes than internet-delivered ACT. Participants with chronic headache and fibromyalgia showed greater benefit from ACT compared to those with non-specific pain or mixed pain. In addition, the longer the follow-up duration, the smaller the effect sizes for pain intensity/physical function at follow-up. The present meta-analysis suggests sufficient evidence for the significant benefits of ACT for people with chronic pain.