Background:Congenital heart defects are the result of incomplete heart development and, like many diseases, have been associated with high homocysteine concentration, Aim and objectives: the aim of the study is to evaluate serum folate and cobalamin levels in children with CHD with correlation to maternal level, Subjects and methods: a prospective study (case-control) carried out from January 2019 to December 2019.The study was conducted on 60 children (males & females) and their mothers , from pediatric cardiology unit and outpatient clinic of Benha University Hospital, was subdivided into; Group (I): Which included 40 children diagnosed as congenital heart defect and their mothers as study group,Group (II): Which included 20 healthy children and their mothers as control group, Results: infant and maternal homocystiene ≥9.65 and ≥11.25 respectively can significantly differentiate cyanotic from acyanotic CHD patients. AUC were 0.964 and 0.808 for infants and maternal values respectively. The sensitivity and specificity for infant homocystiene were 95.2% and 89.5% respectively, while maternal cutoff value had a sensitivity and specificity of 90.5% and 63.2% respectively, Conclusion; a high maternal tHcy concentration is associated with an increased risk of having a child with CHD in a concentration‐dependent manner, partially due to low serum folate and vitamin B12. The folate status of the child might be involved as well and should be investigated together with other pathways implicated in CHD, Keywords: Homocysteine Folicacid, Methylenetetrahydrofolate reductase, Methioninesynthase, Cystathionine-β-synthase and Congenital heart defect.