Background: Prevention and optimal treatment of postoperative bleeding are of great clinical importance in various types of surgeries including coronary artery bypass graft (CABG). Reducing the amount of bleeding will reduce the complications subsequent to blood transfusion. The positive effects of coagulation factors, especially fibrinogen, after cardiovascular bypass could have beneficial effects due to reduced bleeding and less need for blood transfusion. However, different studies have reported controversial findings.Objectives: The present study aimed to evaluate the effect of prophylactic administration of fibrinogen on blood loss in patients undergoing CABG surgery to achieve more accurate clinical outcomes.Methods: This was a double-blind randomized clinical trial conducted on 36 patients hospitalized in Ahvaz Imam Khomeini Hospital for coronary artery bypass graft. Patients were randomized to receive either fibrinogen concentrate (n = 18) or placebo (n = 18). Hemoglobin, hematocrit, international normalized ratio, prothrombin time, partial thromboplastin time, and fibrinogen were checked preoperatively. The transfusion of allogeneic blood components and the volume of blood loss were recorded and compared between the groups.Results: Prophylactic fibrinogen injection reduced the need for blood transfusion, blood products, and postoperative hypotension in the fibrinogen group when compared to the control group (P ≤ 0.005). There was a significant difference between the two groups in terms of the amount of bleeding during operation (P ≤ 0.005).Conclusions: Fibrinogen plays a key role in preventing and stopping the bleeding. Accordingly, fibrinogen decreases bleeding and the need for paced cell in patients in CABG. Given the adverse outcomes of bleeding and coagulopathy in patients undergoing surgery, we conclude that the use of fibrinogen could be beneficial as a prophylactic in hemorrhagic surgery.