Purpose: The purpose of this study was to evaluate the efficacy of incentive spirometer (IS) and active cycle of breathing techniques (ACBT) following coronary artery bypass graft (CABG) surgery. Material and methods: Sixty male patients (41-75 years) with CABG were included in this prospective randomized study. Thirty patients underwent ACBT and 30 patients underwent IS combined with mobilization. Patients were evaluated using pulmonary function tests, arterial blood gases, 6-minute walk test (6MWT), chest radiography, and a 10-cm visual analogue scale for pain perception. Results: Fifth day post-operatively, pulmonary function variables were similarly but significantly decreased in both groups compared to pre-operative values ( vital capacity decreased 15% and 18% in ACBT and IS, respectively, p<0.05). First day post-operatively, there was significant increase in oxygen saturation after the treatments in both groups. Incidence of atelectasis and pain perception was similar between the groups (p>0.05). No significant difference was found in 6MWT distance obtained before and on the fifth day following CABG surgery within and between ACBT and IS groups (p>0.05). Conclusion: Both treatments improved arterial oxygenation from the first day post-operatively. After a 5-day treatment, functional capacity was well preserved with the usage of ACBT or IS. Both physiotherapy methods had similar effects on the rate of atelectasis, pulmonary function, and pain perception.