Elongation-derotation-flexion Mehta casts are commonly used in the treatment of early onset scoliosis (EOS). We developed a novel suspension bending cast (SBC) technique that enables coronal correction through suspension-assisted bending and rotational correction through molding. The aim of this study was to evaluate the long-term outcomes of SBC at a single institution and to identify prognostic factors associated with curve improvement. A retrospective review was conducted on 49 patients with EOS who underwent SBC between 2011 and 2023. Inclusion criteria included initiation of casting under the age of 10 and a minimum follow-up period of 2 years. Cobb angles were measured before the first cast, after the first cast, at the end of the last cast, and at final follow-up. Rib phase and rib-vertebral angle difference (RVAD) prior to initial casting were also measured. We analyzed rib phase, RVAD, curve improvement, and the type of scoliosis diagnosis. The median age at initial casting was 44 months. The median number of casts was 3, and the median follow-up period was 58 months. The time from the first cast application to surgery was 38.6 months. Of the 49 patients, 31% went from cast treatment to definitive fusion, and an additional 31% underwent additional surgery before definitive fusion. The median Cobb angle was 63° before casting, improved to 21° after the first cast, but progressed to 67° at the final follow-up. The improve group showed a significantly higher initial correction rate compared to the unchange and worsen groups. Idiopathic scoliosis group demonstrated a significantly greater initial correction than non-idiopathic group. No significant differences were observed in final Cobb angle or correction rate based on rib phase or RVAD. The suspension bending cast showed high initial correction in patients with moderate to severe EOS and contributed to delaying surgical intervention. A higher correction rate after the first cast was associated with long-term curve improvement, indicating that initial correction of casting may be an important prognostic factor.