Nutritional deficiencies are estimated to affect at least one third of the world’s population. Although they are most common in developing countries, they are also found in the developed world where they often occur in the setting of alcoholism, eating disorders, post bariatric surgery, and malabsorptive disorders. Neurologic manifestations of vitamin deficiencies are varied, reflecting the diversity of biochemical activity of vitamins throughout the nervous system. Here the neurological manifestations of common vitamin deficiencies are examoned, beginning with a discussion of relevant biochemistry and pathophysiology of each respective vitamin. Several micronutrients are included in the tables within this chapter.