Background: the left internal mammary artery (lima) is commonly utilized as a conduit in coronary artery bypass grafting (CABG). The optimal approach for LIMA harvesting remains debated. In this study, we aimed to assess and compare the early morbidity and mortality in patients undergoing LIMA harvesting for CABG with or without pleurotomy. Methods: A prospective cohort investigation was conducted on 96 patients with ischemic heart disease who underwent elective CABG surgery at a single unit of the cardiothoracic surgery Department, Zagazig University, from January 2018 to December 2022. Patients were split evenly (n=48) between the CP and OP groups. Demographic characteristics, post-operative ventilation time, hospital and ICU stays, post-operative complications, and pulmonary function test results were evaluated and analyzed across two groups. Results: The CP group had significantly shorter ventilation time, ICU, and hospital stays than OP group (5.1±0.68 vs. 7.6±1.64 hours, 2.1±0.28 vs. 3.3±0.66 days, 5.1±0.27 vs. 8.5±0.74 days; p=0.0001 respectively). CP group also had a lower post-operative complication, including pleural effusion and lung atelectasis. Pulmonary function test results showed a significant difference in post-operative forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) among two groups, with better outcomes observed among CP group. Conclusion: This study implies that closed pleura LIMA harvesting may have superior early post-operative outcomes than open pleura harvesting. The CP group experienced shorter ventilation time, ICU, and hospital stays, as well as a lower post-operative complication. These findings support the consideration of closed pleura LIMA harvesting as a preferred technique for CABG surgery.