Introduction & Objective: Post operative bleeding is an important problem following cardiopulmonary bypass (CPB). In normothermic condition may, CPB improve the function of coagulation factors and maintain hemostasis; thus decreasing post-operative bleeding. This study aimed to compare post-operative bleeding and blood products requirements following coronary artery bypass grafting (CABG) in hypothermic and normothermic CPB groups. Materials & Methods: This randomized trial performed on 63 candidates of primary isolated CABG. Patients were randomly divided in to normothermic (N) and hypothermic (H) groups. In group H, the temperature was lowered to 30˚ and mean arterial pressure (MAP) was maintained in the range of 40-65 mm-Hg. In the group N, patients did not cool down actively and the temperature was kept in the rang 35˚-37˚ and MAP was maintained between 60-90 mm-Hg. Blood loss and blood products requirement assessed 12 and 24 h post operatively. Results: There was no statistically significant difference in age, weight, pre-operative LVEF, number of affected coronary arteries, NYHA class, and CPB time between two groups. Blood loss during first 12 and 24 post operative hours were, respectively 395.67 ml and 512.67 ml in group N and 441.82 ml and 626.97 ml in group H (P=0.1 and 0.5 respectively). The mean values of PT and PTT times 6 hours post operation were not statistically different between the two groups, but the platelet count was significantly higher in group N (P=0.003). There was no significant difference in the blood products utilization. Conclusions: Our data suggests that hypo- and normothermic CPB does not influence post-operative blood loss during the first 24 hours in the patients undergoing primary isolated CABG. The only significant difference between the two groups was platelet count which did not result in increased platelet requirement.