We aimed to examine the possible association role of vitamin D and vitamin D receptor (VDR) single nucleotide polymorphisms (SNPs) in type 1 diabetes mellitus (T1DM) development, glycemic control and complications among a cohort of Egyptian children. A prospective case-control study has been conducted on 50 Egyptian children with T1DM who were comparable with 50 controls. Vitamin D and HbA1c were measured. VDR-SNPs [I (rs7975232), I (rs731236) and I (rs1544410)] detection was done by polymerase chain reaction through restriction fragment length polymorphism (PCR-RFLP) technique. Vitamin D supplements were given to the included T1DM children with low vitamin D and reassessments of both HbA1c% and 25(OH)D serum levels were performed in those children three months later. Eighty percent of the included diabetic patients have poor glycemic control. Vitamin D was deficient in 68% and insufficient in 16% of diabetic patients. Significant improvements in both vitamin D and glycemic status among T1DM children, who have low vitamin D and received vitamin D supplementations. There were significantly negative correlations between serum levels of vitamin D with both HbA1c % (r= -0.358, ˂0.05) and daily insulin dose (r=-0.473, ˂0.05). Compared with controls, T1DM children presented more commonly with I a allele (OR: 2.87; 95%CI: 1.39-5.91, ˂0.05) and I b allele (OR: 4.38; 95%CI: 2.30-8.33, ˂0.05). I t allele wasn't significantly differing among patients and controls (˃0.05). Aa+aa and Bb+bb genotypes were significantly higher among T1DM vs the controls (OR: 3.08;, 95%CI: 1.33-7.15, ˂0.05 and OR: 9.33; 95%CI: 3.61-24.17, ˂0.05respectively). I and I were associated with risk of T1DM development among Egyptian children. Low vitamin D status was frequently occurring among T1DM with significant improvement in the glycemic control of such children when adding vitamin D supplements to the standard insulin therapy.