Vitamin D deficiency is associated with a higher risk of multiple sclerosis and also with a higher relapse rate as well as a higher number of MRI lesions. Elders with vitamin D deficiency have worse cognitive performance. Vitamin D deficiency is a risk factor for developing Alzheimer's disease. Ischemic stroke are more frequent and more severe in patients with low vitamin D levels. Carotid atherosclerosis is more frequent and more severe in patients with vitamin D deficiency. Vitamin D deficiency is associated with a higher risk and worse prognosis of Parkinson's disease. In the different neurological disorders discussed herein, gene polymorphisms that could alter vitamin D metabolism are also associated with a higher incidence or a worse disease prognosis. Despite the links between vitamin D deficiency and the risks of developing neurological disorders, there is, to date, no proof that supplementation could alter the course of these diseases.