Coronary artery bypass grafting (CABG) leads to reperfusion syndrome, driven by oxidative stress and lipid peroxidation (LPO). This study investigated the relationship between intraoperative hemolysis (IOH) and oxidative stress in CABG patients. Based on free hemoglobin (Hbfree) levels, 123 patients were categorized into three groups: no IOH (Hbfree ≤ 0.1 g/L, n=43), low IOH (0.1–0.5 g/L, n=42), and high IOH (≥0.5 g/L, n=38). LPO markers (diene conjugates [DC], malondialdehyde [MDA]) and antioxidant defense factors (α-tocopherol, retinol) were analyzed. Postoperatively, LPO product levels increased significantly in all groups, with the highest levels in the high IOH group (p<0.001). Antioxidant levels were lowest in this group, indicating oxidative stress activation. Findings suggest that reducing intraoperative hemolysis could mitigate oxidative stress and related complications. Perioperative strategies should focus on enhancing antioxidant defenses and minimizing oxidative damage in CABG patients.