BACKGROUND: Scars with poor cosmesis that develop after wound healing may affect normal life. OBJECTIVE: To assess the efficacy and safety of botulinum toxin type A (BTXA) in preventing postoperative hypertrophic scars or keloids. METHODS: A systematic review was performed by searching the PubMed, Cochrane Library, and EMBASE databases from their inception date up to February 2020 for randomized controlled trials (RCTs) evaluating the efficacy of BTXA in preventing hypertrophic scars or keloids. The primary outcome measures included the Vancouver Scar Scale (VSS) score, Visual Analog Scale (VAS) score, scar width, patient satisfaction, and adverse events. RESULTS: Twelve RCTs involving 497 cases (372 patients) were included. The meta-analysis showed significant differences in the VAS score (weighted mean difference [WMD] = 1.31, 95% CI = 1.06 to 1.55, < .00001), VSS score (WMD = -1.02, 95% CI = -1.72 to -0.32, = .004), scar width (WMD = -0.18, 95% CI = -0.29 to -0.08, = .0008), and patient satisfaction (relative risk = 1.25, 95% CI = 1.06-1.49, = .01). Four studies reported trivial adverse events. CONCLUSIONS: This meta-analysis showed that BTXA was more effective than the control treatment in preventing postoperative scars and improving the cosmetic appearance of facial scars for East Asians, and no serious adverse events were found during the follow-up period. However, there was insufficient evidence to support the use of BTXA for the prevention of scars in patients from other ethnic groups and regions or scars in non-facial areas.