We report a case of transfusion-related acute lung injury (TRALI) during coronary artery bypass surgery. A 73-year-old man developed severe hypoxemia after transfusion of platelet concentrate just before completion of surgery. The possibility of cardiogenic pulmonary edema was excluded by transesophageal echocardiography. A chest X-ray showed bilateral pulmonary edema, suggesting TRALI. Steroid therapy and administration of sivelestat sodium hydrate and vasopressors were started. The patient's PaO2 /FIO2 ratio increased from 56 to 223 within 12 hrs. Anti-HLA and antigranulocyte antibodies were detected in the donated blood products. We assume that the cause of this case was an immune reaction through anti-HLA and/or antigranulocyte antibodies. TRALI is a potentially life-threatening, underrecognized and under-reported complication of transfusion. A better understanding and awareness is needed for medical staffs.