Carbamoyl phosphate synthetase 1 deficiency (CPS1D) is an autosomal recessive disorder of the urea cycle that causes hyperammonemia. Severe hyperammonemia in patients with neonatal CPS1D leads to serious brain damage, coma, and death if not treated promptly. Despite the improvement of treatments, including continuous hemodialysis, ammonia-lowering agents, and a low-protein diet, the overall outcome of severe hyperammonemia still remains disappointing. As the liver is the only organ in which ammonia is converted into urea, the conventional liver transplantation (LT) has been considered as an elegant and radical alternative therapy to classical dietary and medical therapies. However, LT has many disadvantages, such as a considerable risk for technical complications and perioperative metabolic derangement, especially in neonates. Additionally, there is a lack of suitable donor organs in most countries. According to recent studies, hepatocyte transplantation (HT) is a therapeutic option and serves as a bridge to LT. Here, we report a Korean CPS1D patient with novel mutations in CPS1 who was treated by HT. Four-day-old male infant with severe hyperammonemia was transferred to neonatal intensive care unit and treated with continuous renal replacement therapy (CRRT) and ammonia-lowering agents (sodium benzoate and sodium phenylbutyrate). Because of repeated episodes of hyperammonemia, three times of HT were conducted at the age of 1 month. With additional HT at the age of 6 months, he had shown a good neurodevelopmental outcome without hyperammonemia episodes that need CRRT. In conclusion, HT is well tolerated and could be a possible therapeutic option to control hyperammonemia in patients with CPS1D.