Aim: To assess the effectiveness of decision aids in the treatment, prevention and screening of breast cancer patients. Design: A systematic review and meta‐analysis. Methods: The review protocol was registered in the CRD Prospero database(CRD42020173028). A literature search was carried out in five databases: PubMed, Cochrane, EMBASE, Scopus and Web of science data in January 2020. We used The Cochrane risk bias assessment tool to evaluate the literature quality of included trials and the Review Manager 5.2 software to analyse data. Results: We included 22 studies. Compared with the conventional methods, decision aids reduced treatment decision conflicts and had no significant effect on screening decision conflicts (WMD=−2.25, 95% CI = ‐ 2.64,‐1.87, p <.0001; WMD=−1.37, 95% CI = ‐ 3.57,0.83, p =.22). Three were no statistical differences in participants' anxiety, decision regret, knowledge, informed choice and decision‐making satisfaction between the two groups. [ABSTRACT FROM AUTHOR]