Idiopathic thrombocytopenic purpura (ITP) is an autoimmune condition characterized by increased platelet destruction. Although the etiology of ITP remains unclear, it is accepted that both environmental and genetic factors play an important role in the development of the disease. Many gene polymorphisms have been reported to be closely associated with the susceptibility to ITP. The current study aimed to investigate the association between the DNA methyltransferase; DNMT3B-579 G/T promoter polymorphism and the risk for acquisition of pediatric ITP in a cohort of Egyptian children. Genotyping of the studied gene by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) assay was conducted on 70 ITP patients and 100 healthy controls and revealed that DNMT3B-579 TT homotype was significantly higher in ITP patients and conferred two fold increased risk of ITP (OR = 2.23, 95%CI = 1.29-3.86). The mutant T-allele was significantly higher in ITP patients and was associated with increased ITP risk (OR= 1.35, 95%CI= 1.06-1.71). There was no statistically significant difference in the clinical or laboratory data between ITP patients with wild or mutant genotypes. Moreover, there was no statistical difference in the distribution of DNMT3B-579 G/T genotypes between the acute and chronic ITP patients. In conclusion, this genetic polymorphism can be considered as molecular marker for ITP risk among Egyptian children, but not a molecular predictor for chronicity.