Objective: Studies determining the relationship between serum vitamin D status and childhood asthma have yielded controversial results. Findings indicated that vitamin D deficiency is associated with asthma and airway hyper responsiveness. The aim of this study was to assess the relationship between serum vitamin D status and childhood asthma., Methods: Data were obtained from 200 asthmatic children (age 3-12 years) and 200 healthy controls. Serum levels of 25(OH) vitamin D, total IgE, calcium, phosphorus, parathormone (PTH) and eosinophil count were measured in both asthmatic children and healthy controls. Also, the mean values of 25(OH) vitamin D were compared with asthma symptom severities., Findings: There was a significant decrease in the concentration of serum 25(OH) vitamin D in the asthmatic patients as compared with the controls (20.34±2.8 vs 25.39±4.1 ng/mL, 95%CI: 1.46-3.86, P=0.01). Out of total asthmatic subjects, 40 (20%) were vitamin D sufficient, 48 (24%) were insufficient, and 112 (56%) were deficient. Total IgE concentration was also significantly higher in asthmatic patients having vitamin D deficiency (132.4±20.1 IU/ml, 95%CI: 1.38-3.75, P=0.03). Comparing asthmatic patients with healthy controls, odds of having vitamin D level less than 20ng/mL was 2.47., Conclusion: Our findings suggest that vitamin D deficiency or insufficiency may be positively related to the prevalence of asthma in children.