Abstract Background: Crigler-Najjar syndrome (CNS) is an uncom-mon autosomal recessive hereditary condition characterized by severe unconjugated nonhemolytic hyperbilirubinemia from infancy. It is caused by a defect of bilirubin uridine diphosphate glucuronosyltransferase (UGT) 1A. Aim of Study: We aimed to identify mutations in exons (2-4) in the UGT1A1 gene in Egyptian CNS patients. Material and Method: The UGT1A1 gene's exons (2-4) were then molecularly examined using PCR amplification and singe sequencing of the coding regions after ten Egyptian CNS patients had been clinically identified. Results: The patients were between the ages of 3 and 18, with an average age of 8.3±4.74 years. All patients (100%) had positive consanguinity, and 50% of cases had positive family history. Forty percent of the patients had delayed verbal and/ or social or motor milestones, whereas the remaining sixty per-cent of patients had normal developmental milestones (6/10). The aggressive behavior exacerbates the illness. CNS type I affected 10 patients (100%) while type II affected 0 instances (0%). No deleterious mutations were found in exons (2-4) of UGT1A1 gene. Conclusion: This study found no mutations in the three studied exons (exons 2-4) of the UGT1A1 gene. This highlights the importance of studying the rest of the exons of the UGT1A1 gene.