The current study was carried out systematically by conducting a review of the literature. The purpose of this study was to conduct a systematic review of the literature to determine the effects of brace wearing on sagittal parameters in adolescents with idiopathic scoliosis (AIS). In this study, PubMed/MEDLINE (National Library of Medicine), Scopus, Ovid, CINAHL, PEDro, Google Scholar, and the Cochrane Library were accessed and searched using the patient, intervention, comparison, outcome, and study design model. We included studies that looked at the effects of brace treatment on sagittal spinopelvic parameters in AIS patients over the age of 18. The studies were chosen for their cross-sectional, retrospective, or prospective observational designs, and they were published in English. Review articles, case reports, case study designs, and conference abstracts were excluded from consideration. The methodological quality of the remaining articles was assessed using the Newcastle Ottawa Scale. A total of 12 studies were chosen, and 995 participants were evaluated, with 3 (25%) and 9 (75%) having high and moderate quality, respectively. The studies were classified based on the length of follow-up. Long-term, short-term, and immediate effects of brace wearing on sagittal spinopelvic parameters were reported in four, five, and three studies, respectively. The results of nine studies showed a significant decrease in Cobb angle after wearing the brace, which contradicted the findings of the other two. The cervical and sagittal pelvic parameters, thoracic kyphosis (TK), lumbar lordosis (LL), spinopelvic parameters, and sagittal balance were all evaluated in the intended studies, yielding varying results. According to the available literature, wearing a brace flattens the TK and LL. According to this systematic review, brace treatment may affect sagittal spinopelvic parameters in adolescents with AIS, particularly in TK and LL. The cervical and pelvic parameters yielded inconclusive results. This study backs up the idea that brace design and structure can influence sagittal parameter changes. The limitations of this study include different methods of parameter measurement, variations in the brace types and wear time, varying follow-up duration, and differences in participant characteristics.