Background: Generally, rounded shoulders may occur when an individual habitually takes a relaxed, slouched posture. Although various studies on the round shoulder exist, studies on the effect of improvement of thoracic mobilization on the round shoulder are insufficient. Objectives: To investigate the effect of thoracic mobilization on round shoulders and pulmonary capacities. Design: Randomized controlled trials. Methods: Twenty subjects were randomly allocated into an exercise group (n=10) and a mobilization group (n=10). To quantify the round shoulder before and after the intervention, the distance between the acromion and the table surface was measured, and the pulmonary capacities were also measured. The intervention program was conducted twice a week for 6 weeks. The exercise group performed corrective exercise, and the mobilization group performed both corrective exercise and thoracic mobilization. Results: The round shoulder in both groups was significantly decreased (P<.05), and the pulmonary capacities were significantly improved (P<.05). However, there was no significant difference between the two groups (P>.05). Conclusion: The combination of corrective exercise with stretching and strengthening exercises led to the improvement of round shoulders and pulmonary capacities, no additional benefits were detected with thoracic mobilization.