Background & Aim: Identification of 25(OH) Vit D receptors in endothelial cells, smooth muscle cells, and myocytes from the heart has led to the hypothesis that this 25(OH) Vit D is involved in cardiovascular disease. The present study was designed to evaluate 25-hydroxy Vitamin D serum levels in congenital heart disease (CHD) children compared to controls. Methods: This case control study included 100 children, divided into 2 groups, Group (A) included 60 children with CHD who were divided into two groups (cyanotic and acyanotic). And group (B) included 40 apparently healthy children as a control group. All patients included in the study were subjected to the following: complete history taking and physical examination, echocardiography, and serum 25 (OH) vitamin D levels. Results: The mean serum.25 (OH) vitamin D level was significant lower in the CHD group than control group . the Serum.25 (OH) vitamin D level was significant lower in cyanotic group than acyanotic patients . there were a statistically significant difference between Serum.25 (OH) vitamin D level with various age groups of cyanotic and acyanotic patients. Conclusion: The serum level of 25(OH) Vit D was lower in CHD children, and among the patients, was lower in cyanotic. So it should be checked in CHD children especially those who suffered from cyanotic heart disease.