Background: 1, 25-dihydroxy vitamin D3 (VitD3) can improve the effect of allergen-specific immunotherapy (SIT). Few data is available about its role in childhood asthma. Objective: To assess the immunological and clinical efficacy of VitD3 as an adjuvant to allergen specific immunotherapy in pediatric asthma. Methodology: Sixty nine children with atopic asthma were divided into three groups: a group received subcutaneous immunotherapy (SCIT) in combination with VitD3 (n=23), another group received SCIT alone (n=23), and the last group VitD3 alone (n=23). All children were assessed at baseline, and six months for rate of inhaled corticosteroid (ICS) discontinuation, and serum levels of IL-10, and IL-17A. Results: In the SCIT + vitD3, ICS discontinuation rate was higher compared to VitD3 alone group and SCIT alone group at the end of 6th month (P=0.555 and 0.016 respectively). The combined SCIT+ VitD3 group showed significant increase of serum IL-10 level in comparison to SCIT alone group and VitD3 alone group (P=0.000) and significant decrease in serum IL-17A level compared to VitD3 alone group (P= 0.011) Conclusion: VitD3 enhance the clinical and immunological outcomes of SIT in pediatric asthma. Further investigation is needed to evaluate this effect in a larger scale to confirm its role as an adjunct to SIT.