PurposeThe aim of this study was to investigate the effect of incentive spirometer exercise (ISE) on pulmonary function and maximal phonation time (MPT) in children with spastic cerebral palsy (CP).Materials and MethodsFifty children with CP were randomly assigned to two groups: the experimental group and the control group. Both groups underwent comprehensive rehabilitation therapy. The experimental group underwent additional ISE. The forced vital capacity (FVC), forced expiratory volume at one second (FEV1), FEV1/FVC ratio, peak expiratory flow (PEF), and MPT were assessed as outcome measures before and after 4 weeks of training.ResultsThere were significant improvements in FVC, FEV1, PEF, and MPT in the experimental group, but not in the control group. In addition, the improvements in FVC, FEV1, and MPT were significantly greater in the experimental group than in the control group.ConclusionThe results of this randomized controlled study support the use of ISE for enhancing pulmonary function and breath control for speech production in children with CP.