Routinely, adolescent idiopathic scoliosis (AIS) curves that progress beyond 40° in skeletally immature adolescents require surgery. However, some adolescents with AIS and their parents utterly refuse surgery and insist on wearing a brace. Debate continues regarding the appropriateness of bracing for AIS curves exceeding 40° in patients who have rejected surgical intervention. This systematic review and meta-analysis was conducted to review the literature on the effectiveness of bracing and its predictive factors in largermagnitude AIS curves ≥40°. This study replicated the search strategy used by the PICOS system for formulating study questions, which include consideration of the patient/population (P), intervention (I), comparison (C), outcome (O), and study design (S). The search was conducted up to January 2022 in the following bibliographic online databases only in the English language: PubMed, Google Scholar, Scopus, and Web of Science. Two assessors reviewed the articles for qualification. Eligible studies were assessed for risk of bias at the study level using the Newcastle-Ottawa Scale. The effect size across the studies was determined using standardized mean differences (Cohen’s d) and 95% confidence intervals for the meta-analysis. Among the eight included moderate quality studies, evidence of potential publication bias (p <0.05) for the trials included was found in the Cobb angle outcome. Results obtained through meta-analysis indicated that the effectiveness of bracing in controlling Cobb angle progression in curves ≥40° is significantly positive. Additionally, initial curve severity, Risser stage, in-brace curve correction, curve type, and apical vertebral rotation were considered risk factors associated with brace effectiveness. This systematic review revealed that bracing could alter the normal course of AIS curves ≥40° in patients refusing posterior spinal fusion (PSF). However, the suggested course for patients refusing PSF remains unclear because of the significant heterogeneity in the risk factors associated with bracing failure.