Multiple sclerosis is a chronic, inflammatory, demyelinating disease which affects the central nervous system and is linked to autoimmune disorders. Although the precise causes of multiple sclerosis remain unknown, some evidence points towards hypovitaminosis D. Apart from the maintenance of calcium and phosphorus homeostasis, vitamin D also plays a major role in other aspects of human health. It is caused by the vitamin D receptor, which is present in many human organs and tissues. Vitamin D is an immunomodulating factor and accordingly has a potential to be effective in both preventing and treating autoimmune diseases, including multiple sclerosis. The aim of this review was to present up-to-date knowledge about vitamin D, especially its impact on risk of multiple sclerosis onset, relapses, and potential to modify the immune response. A further objective was to describe the role of vitamin D supplementation and its provision in the everyday diet for both prevention and treatment of multiple sclerosis.