Transfusion associated graft-versus-host disease is a rare but fatal disease reported after open heart surgeries mainly in Asian people. It can be prevented by pretransfusion gamma irradiation of the fresh whole blood. In this presentation, we report a case of transfusion associated graft-versus-host disease following coronary artery bypass surgery in a 61 year-old male patient. Postoperatively the patient was transfused urgently with 2 units of fresh whole blood from his two sons. He was discharged on postoperative 10 day with only symptom of mild diarrhea. Two days after discharge, he was readmitted because of persistent diarrhea, systemic erythema and high fever. On laboratory examinations, he showed findings of failure in liver, kidney, gastrointestinal tract, and bone marrow. Hemodynamically he deteriorated acutely and died of multiple organ failure on 17th postoperative day. This has been our first experience since we started open heart program at our hospital and we changed our policy for the transfusion of the fresh whole blood after this event.