Background: Coronary artery disease (CAD) is one of the most prevalent non-communicable diseases in Sri Lanka. Coronary Artery Bypass Graft Surgery (CABG) is considered as the main revascularization procedure in patients with CAD. Cardiac rehabilitation is a multiphasic and multi-disciplinary program and is considered as a significant component of postoperative management after CABG. Objective: To study the effect of obesity on Cardiac Rehabilitation Program II (CRPII), a 1-month period of cardiac rehabilitation following discharge from the hospital, in patients who have undergone CABG. Methods: This was a prospective analytical study involving a convenient sample of 100 patients after CABG surgery. The patients (age: 40-70 years, both males and females) were selected from the cardiac rehabilitation program of the Cardiology Unit at the National Hospital of Sri Lanka. Data collection was done using 5 interviewer based questionnaires: socio-demographic characteristics using socio-demographic questionnaire, cardio-vascular endurance and fatigue levels using 6 minute-walk test (6MWT) and Borg scale (BS), anxiety and depression levels using Hospital anxiety and depression scale (HAD) and overall quality of life using quality of life questionnaire cardiac version (QOL). Data collection 1 was done on the first day of CRPII and data collection 2 was done on the final day of the program. Results: There were 33% obese and 67% non-obese patients in the study population. Both groups showed a statistically significant improvement (p<0.0001) of 6MWT, BS, HAD and QOL after CRPII. There was a significant difference (p<0.05) in the improvement of 6MWT in the non-obese group compared to the obese group and there was no difference in BS, HAD and QOL between obese and non-obese groups. Conclusions: CRPII led to an improvement in cardiovascular endurance, anxiety/depression and overall quality of life in patients who underwent CABG. Non-obese patients showed a better improvement in cardiovascular endurance compared to obese patients after CRPII.