Vitamin D is commonly known for its role in calcium-phosphate metabolism but there is growing amount of data showing its pleiotropic actions. Positive correlation between vitamin D deficiency and the prevalence of autoimmune diseases including multiple sclerosis, rheumatoid arthritis, systemic lupus erythematosus, etc. has been observed. Vitamin D receptors have been found in spectrum of tissues and organs, including bones, muscles, reproductive organs, heart, brain, and within the immune system. Widely investigated immunomodulatory action of vitamin D affects both innate and adaptive immunity by suppressing T cell proliferation and cytotoxity, promoting regulatory T cells differentiation and modulating macrophage and dendritic cell functions. Multiple sclerosis(MS) is an autoimmune disease of the central nervous system caused by complex and predominantly unknown interactions of genetic susceptibility and environmental factors. Epidemiological studies show that the sun exposure and corresponding vitamin D level are important factors that can explain geographical distribution of MS. Some preliminary observations suggest that vitamin D supplementation not only reduces the risk of developing MS but also modulates disease course and reduces relapses rate among patients with relapsing-remitting MS. Further studies and clinical trials are required to confirm the role of vitamin D in MS pathogenesis.