There are considerable public concerns about the relationship between mobile phone radiations and human health. The present study assesses the effect of electromagnetic field (EMF) emitted from mobile phone on the immune system in rats and the possible protective role of vitamin D. Rats were randomly divided into six groups. Group I: control group, Group II: Received vitamin D (1000 IU/kg/day) orally, Group III: Exposed to EMF 1h/day, Group IV: Exposed to EMF 2h/day, Group V: Exposed to EMF 1h/day and received vitamin D (1000 IU/kg/day), Group VI: Exposed to EMF 2h/day and received vitamin D (1000 IU/kg/day). After 30 days of exposure time, 1h/day EMF exposure resulted in significant decrease in immunoglobulin levels (IgA, IgE, IgM and IgG), total leukocyte, lymphocyte, eosinophil and basophil counts and significant increase in neutrophil and monocyte counts. These changes were more increased in 2h/day EMF exposed group. Vitamin D supplementation in EMF-exposed rats reversed these results when compared to EMF-exposed groups. In contrast, 7, 14 and 21 days of EMF exposure produced non-significant difference in these parameters among all experimental groups. We concluded that exposure to mobile phone radiations compromises immune system of rats and vitamin D appears to have protective effect.