Multiple sclerosis (MS) is a chronic demyelinating disease and also is one of the most common disabling neurological disorders in young and middle-aged adults. The main pathogenesis of MS has long been thought to be an immune mediated disorder of the central nervous system. The function of the immune system is under the influence of vitamin D which as a modulator of immune response could play a role in autoimmune diseases including MS. Deficiency of vitamin D or variations in DNA sequence (polymorphism) of vitamin D receptor gene diminishes its optimal function on immune system that consequently could lead to increasing risk of MS. However, its role in development and modulating the course of MS is still under investigation. In this review we aimed to discuss the role of vitamin D in body, immune system and consequently altering the risk of MS.