Patients with inborn errors of metabolism undergo liver transplantation, but the effect of transplanting the liver of healthy carriers of these conditions has not been fully clarified. A 6-year-old girl with classical citrullinemia, who repeatedly suffered from hyperammonemia, underwent living-related liver transplantation by using a segment of the liver of her mother, who was a heterozygote carrier for classical citrullinemia. Hyperammonemia alleviated in the patient after the transplantation, thereby dramatically improving her quality of life. Although the levels of plasma and urinary citrulline remained high postoperatively, there was no marked difference in the level of plasma citrulline up to 1 month after surgery when compared with that of previously reported orthotopic liver transplantation cases with classical citrullinemia.