Background: Adult scoliosis is a spinal deformity associated with trunk asymmetry and impaired pulmonary function. However, evidence for exercise interventions in adults with scoliosis remains limited. Objectives: To compare the effects of posterior chain sling exercise, Pilates exercise, and their combination on scoliosis angle and pulmonary function in adults in their 20s with scoliosis. Design: Randomized controlled trial. Methods: Thirty-three adults in their 20s with scoliosis were randomly assigned to the Pilates exercise group (n=11), posterior chain sling exercise group (n=11), or combined Pilates and posterior chain sling exercise group (n=11). Each group underwent a 30-minute exercise intervention three times per week for 12 weeks. Scoliosis angle was assessed using the Formetric 4D system, and pulmonary function was assessed by spirometry, including forced vital capacity (FVC) and forced expiratory volume in one second (FEV₁). Assessments were performed at baseline, after 6 weeks of intervention, and after 12 weeks of intervention. Results: Significant group, time, and group-by-time interaction effects were observed for scoliosis angle, FVC, and FEV₁ (P<.05). Post hoc analyses showed significant improvements in all groups, with the combined group demonstrating the greatest improvements. Conclusion: Twelve weeks of Pilates and posterior chain sling exercises reduced scoliosis angle and improved pulmonary function. The combined intervention produced greater improvements in spinal alignment and pulmonary function than either intervention alone.