Crigler-Najjar syndrome (CNs) is a rare hereditary unconjugated hyperbilirubinemia caused by mutations in the bilirubin Uridine (UDP) glucuronosyltransferase family 1 member A1 (UGT1A1, ENSG00000241635) gene. Two patients were clinically diagnosed with Crigler-Najjar Syndrome types II (CNs-II) can be clinically diagnosed which were based on the level of total bilirubin, efficacy of phenobarbital treatment, normal liver architecture and exclusion of hemolysis. Diagnosis was also confirmed by UGT1A1 gene mutations, which by sequencing the coding region for UGT1A1 gene mutations, which were the homozygous mutations c.668G > A/p.Cys223Tyr and which caused less than 10% of activity of the enzyme. No data have been reported about this mutate in the population. These patients have a good prognosis and require no active intervention, indicating that an early accurate diagnosis is necessary for disease management and genetic counseling.