Crigler-Najjar syndrome type 1 (CNS1) is characterized by severe unconjugated hyperbilirubinemia from birth, caused by total failure of UDP-glucuronyltransferase activity. Only liver transplantation (LT) can correct the metabolic defect totally and avoid irreversible neurological deficits. However, because the onset of neurologic deficits is unpredictable, timing of LT remains difficult. In our transplant center, 4 patients underwent living related liver transplantation (LRLT) for CNS1. Three of them were infants (2, 8.5 and 15 months old /5, 8, and 10 kg in weight). The 13 yr patient had no neurodevelopmental sequela except learning difficulties. Three patients’ parents were consanguineous. All patients required extensive phototherapy to control bilirubin levels. The 2 months old baby underwent phototherapy for only two weeks after birth. When he visited our hospital at the age of 2 months, his unconjugated bilirubin level was 30 mg/dl, and he had high pitched cry suggesting bilirubin encephalopathy. Plasmapheresis, intense phototherapy, and early LRLT performed to this patient. Other 2 patients (8.5 and 15 months) were neurologically normal. Three fathers and one mother were the donors. Three patients received left lateral segments and 1 patient received a left lobe. Biliary reconstruction was completed with a duct-to-duct anastomosis. One patient (8.5 months) experienced biliary leak and treated with repeated cholangioplasty. All patients had normal unconjugated bilirubin levels after transplantation.Three patients were alive with normal neurodevelopmental milestones for 1, 8 and 29 months after LRLT. One patient (2 months) displayed kernicterus signs (axial hypotonia, lack of head control, spasticity of lower limbs, feeding difficulties) and died following aspiration of gastric contents 10 months after the operation. In conclusion, Irreversible brain damage (kernicterus) may occur very early in the course of CNS1 disease. Despite urgent treatment modalities like plasmapheresis, phototherapy and LT irreversible brain damage may occur. Because no alternative treatment options are available at this time, LT should be performed as a preventive procedure to counteract severe CNS1-related complications.