Objective To systematically evaluate the intervention effect of acceptance and commitment therapy on breast cancer patients. Methods A systematic search of databases, including the Cochrane Library, Web of Science, PubMed, Embase, CINAHL, PsycInfo, CNKI, WanFang Data and CBM, was carried out to collect randomized controlled trials on acceptance and commitment therapy on breast cancer patients from inception to August, 2021. There were 2 researchers who screened the literature according to inclusion and exclusion criteria, extracted data and evaluated the methodological quality. Meta-analysis was conducted with Revman5.4 software. Results A total of 13 randomized controlled studies were included, involving 1061 patients. Meta-analysis showed that acceptance and commitment therapy was superior to conventional care on improving depression [SMD=-1.15, 95%CI(-1.48, -0.82), P<0.001], anxiety [SMD=-1.28, 95%CI(-1.53, -1.04), P<0.001], psychological flexibility [MD=-12.26, 95%CI(-15.02, -9.51), P<0.001] and post-traumatic growth [MD=-12.48, 95%CI(-13.55, -11.40), P<0.001], and perceived benefit of disease[MD=-8.77, 95%CI(-10.79, -6.75), P<0.001] of breast cancer patients. Conclusion Acceptance and commitment therapy can relieve depression and anxiety, improve psychological flexibility and post-traumatic growth, and enhance the perceived benefit of disease. It plays a positive role in the improvement of mental state of breast cancer patients.