Introduction: Post cardiac surgery hemorrhagic syndromes, potentialized by implementing cardiopulmonary bypass, leads to increased hazards of blood products transfusion and pertains serious impacts on immediate patients outcome. The objective of this clinical trial was to investigate the efficiency of exogenous fibrinogen to control hemorrhagic syndromes following cardiac surgery in the intensive care unit. Materials and Methods: Eighty patients undergoing open heart surgery at Imam Reza Hospital, Mashhad, Iran with blood drainage more than 200 ml per hour were randomly divided to receive either fibrinogen 2 grams or placebo. The patients were investigated for amount of blood drainage, units of required blood product, length of stay in intensive care unit (ICU), and mortality. Results: The first early 3-hours drainage (443.97±169.98 vs 606.66±235.93ml; p value =0.001) and total first 24 hours drainage (1025.30 ml and 1377.60 ml; p value: 0.041) showed significant difference in favor of fibrinogen receiving group. The fibrinogen group required significantly lesser units of red blood cells, and fresh frozen plasma (FFP) (1.62 and 2.55) compared to placebo group (2.74 and 3.21) (p values: 0.010 and 0.032). Platelets units requirement did not reach significant difference between the groups. ICU length of stay was shorter in fibrinogen group (2.82 days versus 4.02 days; p value 0.045), while mechanical ventilation time did not significantly differ among the two groups. In addition, there was a trend towards decreased early mortality in fibrinogen receiving group (7.5% versus 17.5 % ; p value = 0.02). Conclusion: Administration of low dose of fibrinogen in patients with postoperative bleeding can reduce ongoing and total blood drainage, transfusion of blood products, ICU length and early mortality