Background: This study investigated the therapeutic effects of 12-week Schroth rehabilitation exercises (SRE) in improving Cobb’s angle, scoliometer readings, lumbar lordosis, and the calcaneal valgus angle of patients with idiopathic scoliosis. Methods: This pilot study included 60 adolescent patients diagnosed with idiopathic scoliosis by a rehabilitation physician based on a Cobb’s angle of ≥10° using total anteroposterior plain radiography. Patients were classified into groups with a Cobb’s angle of 10–19° (G1), 20–29° (G2), and ≥30° (G3). Cobb’s angle, scoliometer readings, lumbar lordosis, and calcaneal valgus angles were analyzed before and after the 12-week SRE. Results: SRE improved Cobb’s angle (−6.85), scoliometer readings (−2.80), lumbar lordosis (4.23), and calcaneal valgus angles (left, −3.76; right, −2.83) regardless of the initial scoliosis angle, and within-group changes were significant (p < 0.001). In this study, participants in all three groups had undergone SRE, regardless of initial scoliosis severity, and the findings were significant. Conclusion: SRE can be used for patients with idiopathic scoliosis to improve asymmetric musculoskeletal morphology and the patient’s quality of life.