Coronary artery bypass grafting (CABG) can trigger reperfusion syndrome, primarily driven by oxidative stress and lipid peroxidation (LPO). This study examined the association between intraoperative hemolysis (IOH) and oxidative stress in CABG patients. A total of 123 patients were classified into three groups based on free hemoglobin (Hbfree) levels: no IOH (≤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, including diene conjugates (DC) and malondialdehyde (MDA), along with antioxidant defense factors (α-tocopherol, retinol), were analyzed. Postoperatively, LPO product levels significantly increased in all groups, with the highest levels observed in the high IOH group (p<0.001). Concurrently, antioxidant levels were lowest in this group, indicating pronounced oxidative stress activation. These findings highlight the need for strategies to minimize intraoperative hemolysis, enhance antioxidant defenses, and reduce oxidative damage to improve CABG outcomes.