To investigate whether adding diaphragmatic release to corrective exercise could improve the Cobb angle and pulmonary function more than corrective exercise alone in hyperkyphotic adolescent girls. Single-blinded, randomized, controlled trial. 118 adolescent hyperkyphotic girls were allocated randomly into two equal groups. Control group received only corrective exercise, while study group received diaphragmatic release in addition to corrective exercise. Primary outcome was Cobb angle, assessed by lateral radiographs. Secondary outcomes were pulmonary function testing, assessed by computerized spirometery. Outcomes were assessed pre- and post-treatment, after three months of interventions, in both groups. Two-way ANOVA revealed that both Cobb angle and pulmonary function testing significantly improved after treatment in both groups (p < 0.001). Time*group interaction revealed that the study group had a superior improvement in Cobb angle and pulmonary function testing compared to the control group (p < 0.003 and p < 0.001, respectively). Adding diaphragmatic release to three months of multimodal corrective exercise program showed superior improvements in Cobb angle and pulmonary function testing than corrective exercise alone in hyperkyphotic adolescent girls within a shorter timeframe compared to previous studies. These results strengthen the hypothesis of its potential as a beneficial addition to the treatment of thoracic hyperkyphosis.