The most widely recognized postoperative complexities are watched and overseen after abdominal or cardiothoracic surgery are pulmonary complications and it is continue to contribute to patient morbidity and mortality. Hence, this study was conducted with the aim to determine the effectiveness of active cycle of breathing technique on pulmonary complications after coronary artery bypass surgery. Pre-experimental research design was adopted to conduct the study with 20 samples who met the inclusion criteria. Demographic variables were collected by using structured questionnaire and assessed the physiological parameters such as oxygen saturation, respiratory rate, and heart rate, systolic and diastolic blood pressure. Followed by active cycle of breathing technique was administered to the participants twice a day for 3 days from the first post-operative day onwards. Pre and post assessment was done each day before and after the intervention and post-test value was taken for analysis. Post-operative complications were assessed at the end of 3rd day of intervention by using the checklist contains the pulmonary complications due to surgery. Data were analyzed using SPSS statistical package. There was a significant improvement was observed in oxygen saturation, respiratory and heart rate at the level of p<0.05 and the percentage of complications also very minimal. The findings of the study concluded that active cycle breathing technique is effective in pulmonary function thereby prevent the pulmonary complications after coronary artery bypass graft.