Background and Objectives: Adolescent idiopathic scoliosis (AIS) is a prevalent spinal disorder in adolescents. Previous studies have shown biomechanical changes of the gait in the lower limb of AIS patients. To minimize the progression of scoliotic curvature, a spinal brace is used, which has been shown to be efficient. Usually, a brace is worn strictly for 20-22 h every day. To our knowledge, no study has assessed the short- and long-term effects of spinal brace use with or without an exercise program (6 months) to improve clinical and biomechanical parameters. The aim of our study was to verify the effects of short- and long-term spinal brace use, with or without an exercise program on the spine, body balance, and plantar load distribution during gait in AIS. Materials and Methods: A prospective randomized study was conducted with intention-to-treat analysis in forty-five adolescents diagnosed with AIS undergoing conservative treatment at a center specialized in spinal rehabilitation. Adolescents were evaluated at two stages of intervention: (1) spinal orthopedic brace, with acute use 24 h/day (n = 22) and (2) spinal orthopedic brace, with acute use between 15-18 h/day associated with a specific rehabilitation exercise protocol for six consecutive months (six months and 12 total sessions, n = 23). The evaluated parameters were: spine pain, using a visual analog scale (VAS); Cobb angle measurement using radiograph exams, as well as the Risser sign; and static balance and plantar pressure of the feet during gait, carried out using a pressure platform. Results: AIS patients showed significant improvements in the main scoliotic curvature, with a 12-degree reduction in Cobb angle pre- and post-short-term immediate use of spinal brace and a 5.3 degree correction after six months of spinal brace use in combination with specific exercises (long term). In addition, short- and long-term brace use with an exercise program showed a significant increase in anteroposterior and mediolateral balance and a reduction in plantar overload on the heel during gait, with an effect size between moderate and high. Conclusions: Intervention via the short- or long-term use of a spinal brace combined with specific exercises in adolescents with idiopathic scoliosis proved to be effective for correcting scoliotic curvature. In addition, intervention also showed improvements to the antero-posterior and mediolateral body balance and a reduction in the plantar load on the rearfoot region during gait, demonstrating effective mechanical action on the spine.