[Purpose] The aim of this study was to determine the effects of thoracic region self-mobilization on chest expansion and pulmonary function in healthy adults. [Subjects] Nineteen healthy adults were randomly allocated to either an intervention group (n = 8) or a control group (n = 11). [Methods] Subjects in the intervention group performed self-mobilization of the thoracic region 3 times per week for 6 weeks (18 sessions). The outcome measures included chest expansion when breathing, pulmonary function, and predicted pulmonary function. [Results] There was a significant difference in chest expansion between the intervention group and the control group. However, there was no significant difference in pulmonary function between the intervention group and the control group. [Conclusion] Thoracic region self-mobilization may be beneficial for increasing chest expansion in healthy adults.