Older adults are particularly at risk of Vitamin D deficiency due to reduced cutaneous synthesis and intake of Vitamin D. Low Vitamin D levels have been found to be related to a number of diseases frequently found among elderly people, for example, osteoporosis, falls and fractures, sarcopenia, cognitive decline, depression, and cardiovascular disease. However, the evidence to prove the presence of a possible effect of Vitamin D supplementation on age-related diseases is for the most part inconsistent or inconclusive. This chapter reviews and discusses the possible effects of Vitamin D on sarcopenia and other age-related diseases and highlights the need for randomized controlled trials to clarify possible benefits of Vitamin D supplementation in the elderly.