Respiratory muscle function after thoracic surgery may be affected by damage to the muscle, to the nerves or as a result of changes in the mechanics of the respiratory system.There is little information about how respiratory physiotherapy affects the respiratory muscle function after thoracic surgery. The aim of this study was to analyze the effect of respiratory physiotherapy on respiratory muscle strength after thoracic surgery. Forty subjects underwent thoracic surgery were included in this study. The respiratory muscle strength was assessed by measuring maximal inspiratory and expiratory pressures (MIP-MEP) before surgery, on postoperative first day and pre-discharge. Respiratory physiotherapy including breathing exercises, postural drainage, mobilization, postural exercises was applied to all the subjects once a day till to discharge.There was a significant difference between three measurements (p<0, 05). Also a significant difference between preoperative and post-operative first day values of MIP-MEP was found (p<0, 05).There was a significant difference when the post-operative and pre-discharge MIP-MEP were compared (p>0, 05) but the difference was not significant between preoperative and pre-discharge MIP-MEP. The respiratory muscle function of subjects in our study significantly decreased after thoracic surgery. The results of our study showed that respiratory physiotherapy after thoracic surgery prevented the decrease in respiratory muscle strength. Respiratory physiotherapy, especially costal and diaphragmatic breathing exercises may improve the respiratory muscle strength by improving chest wall movements.