Background: Patients undergoing Coronary Artery Bypass Graft (CABG) surgery often develop pulmonary complications in the early post-operative period as result of decreased lung function and impaired cough. Conventional physiotherapy in early post-operative period aims at increasing lung volumes and airway clearance. Objective: This study aimed to determine the effectiveness of the addition of Acapella to conventional chest physiotherapy in improving lung volumes and secretion clearance in early post-operative CABG patients. Methods: Twenty patients of both genders (40–70 years) who had undergone CABG and were in Phase I of Cardiac Rehabilitation were involved in this pilot randomized control trial (9 control, 11 experimental). Post-surgery intervention commenced on post-operative day 2 (POD 2) and continued till POD 6. Patients in the control group were given conventional physiotherapy that included breathing exercises, incentive spirometry and manual techniques. Patient in the experimental group used an Acapella device along with the conventional intervention. Outcome measures considered were pulmonary function parameters (FVC, FEV1 & PEFR) and amount of sputum expectorated. Results: A significant increase in lung volumes was observed in both the groups on POD 6 as compared to POD 2 ([Formula: see text]). However, the increase was significantly greater on POD 6 in experimental group than the control group [mean difference (95% CI) FVC: 0.44[Formula: see text]L (0.24–0.63), FEV1: 0.43[Formula: see text]L (0.19–0.66), PEFR: 0.86[Formula: see text]L/s (0.57–1.14)]. The amount of sputum expectoration significantly greater in the experimental group as compared to the control group [2.71[Formula: see text]mL (0.53–4.90)]. Conclusion: The addition of Acapella enhanced the effect conventional physiotherapy in improving lung volumes and airway clearance in the early post-operative period for CABG patients.