Background: Primary immune thrombocytopenia (ITP) is an autoimmune disorder characterized by autoantibodymediated-enhanced platelet destruction. Chronic ITP was defined as thrombocytopenia persisting for more than 12 months. Previous studies have found that vitamin D receptor (VDR) polymorphisms are associated with the incidence and severity of certain autoimmune diseases. Objective: This study aimed to detect the frequency and role of VDR gene polymorphisms on pathogenesis of chronic ITP in children. Patients and methods: A case control study that was conducted at Hematology Unit of Pediatric, Medical Biochemistry and Molecular Biology Departments at Zagazig University Hospital during a period from November 2017 until November 2018. The study was conducted on 40 participants divided into two groups: case group including 20 children with chronic ITP (8males and 12 females) and control group including 20 age- and sexmatched healthy children (6males and 14females). Results: This study showed that the patients' group had a lower serum vitamin D level than the control group with a statistical significant difference (24.2 ± 9.64 ng/ml and 33.75 ± 11.1 ng/ml respectively). There was also a highly significant difference between chronic ITP cases and control regarding distribution of SNP of VDR gene (Cdx2) where GG was founded in 65% of ITP cases versus 35% in control. Also, AA was founded in 30 % of control versus 5% of cases. Conclusion: Vitamin D receptor gene (Cdx2) polymorphism was found to be associated with higher incidence of chronic childhood immune thrombocytopenic purpura. Also chronic ITP in children was found to be associated with lower level of serum vitamin D.