A 23-year-old woman was admitted to our hospital with jaundice and hepatic coma. She had taken a weight-loss supplement for one month before admission. Her clinical and laboratory findings were consistent with fulminant hepatic failure and fulfilled the criteria of autoimmune hepatitis. Despite corticosteroid pulse therapy and plasma exchange, her symptoms and laboratory findings deteriorated. Her condition improved after she received a living donor-liver transplant from her sister. Autoimmune hepatitis usually follows a chronic course, but it should be considered a type of fulminant hepatic failure and treated promptly.