Background and Objectives: Coronary artery bypass grafting is common in coronary artery disease. Some patients will need a blood transfusion. Despite the known complications of blood transfusions, there are different conclusions about the clinical significance of fresh and non-fresh red blood cells transfusion. Materials and Methods: In this Cohort study, patients were divided in two groups of fresh blood recipients-less than two week blood bag storage-including 744 people and non-fresh-more than two weeks of storage-including 1259 people. Variables including demographic factors, hours of ventilator connection, hours of ICU hospitalization, LVEF, arrhythmia, renal failure, tamponade, neurological deficit, wound infection, septicemia, pneumonia, MI, stroke, pulmonary emboli, and in-hospital mortality were examined in two groups. Results Of the 2003 subjects, 715 (35. 7%) were female and 1288 (64. 3%) were male. According to the Kaplan-Meier curve, the in-hospital survival rate of patients receiving fresh blood was 95. 8% and in non-fresh blood 96. 5%, which did not show a statistically significant difference. In other mentioned variables, no significant difference was observed. Conclusions: Due to the absence of significant differences between mortality and the lifespan of red blood cells in patients undergoing CABG at Tehran Heart Center, it seems that prioritizing fresh blood for the transfusion should be reserved for patients in whom the benefits of fresh blood injections have been proven.