In Japan, living donor liver transplantation has been established as a therapeutic strategy for the rescue of terminal liver disease, including fulminant hepatic failure that shows no signs of recovery. We performed living donor liver transplantation for a subacute type fulminant hepatic failure patient, who had developed a hepatic coma of grade V (no right reflex, no response to pain stimuli). The electroencephalogram indicated almost flat waves. However, cranial computed tomography revealed that brain edema was not severe in this case. The recipient did not have hepatitis virus and had not taken medication that had been determined to cause hepatitis. The recipient was a 12-year-old boy, 165.5 cm in height and 45.5 kg in weight. The donor was his mother, who was 42 years old; her blood type, type B, was identical to that of the boy. The mother's right hepatic lobe was transplanted to her son (the recipient). The post-transplantation condition of recipient was quite excellent. He recovered consciousness 3 days after liver transplantation, and rapidly attained normal hepatic function. The donor was discharged on the 20th postoperative day without any problems. The recipient was discharged on the 79th postoperative day without any neurological deficits. This case suggests that deep coma without electroencephalogram waves may not be a contraindication for living donor liver transplantation in fulminant hepatic failure patients, if the brain edema is not severe.