Background:Bronchial asthma represents one of the common chronic diseases worldwide. The adaptive and innate immune systems play important role in pathogenesis of asthma. Vitamin D has several effects on adaptive & innate immune systems that might be relevant in the protection against or reduction of asthma morbidity, in primary prevention of asthma & in modulation of severity of asthma exacerbations. Several studies suggest there is probable relation between asthma-related symptoms and vitamin D status via the immune modulatory effects of vitamin D.Methodology:A cross-sectional descriptive study was conducted over a period of one and half year duration among 100 cases of bronchial asthma including admitted patients and those attending OPD aged more than or equal to 18 years visiting Bapuji Hospital and OPD, Davangere.Results:This study shows serum vitamin D levels were decreased in asthmatic patients. In case of severe asthmatic patients, serum vitamin D levels were significantly reduced. Asthmatics with vitamin D deficiency showed peripheral blood eosinophilia (674.96±261.1).Conclusion:There is important association between serum vitamin D (both deficiency or insufficiency) and adult bronchial asthma. A strong correlation is also seen between the serum vitamin D level, asthma severity and absolute eosinophil count.