The role of vitamin D in athletes has garnered significant attention in the literature. Given the chronic physical and mental stress the athletes, in particular the elite ones are exposed to, they should be regarded as a distinct population for assessing the vitamin D status. There is unequivocal evidence for the association between low vitamin D levels and different types of sports. Numerous studies have reported a high prevalence of vitamin D inadequacy (insufficiency, deficiency) in professional athletes across a range of sports and geographical areas, particularly in winter and early spring. We provide herein an overview of the single-sport and multiple-sport studies that reported inadequate levels of vitamin D in athletes. In some (but not all) of these studies, association with decreased physical ability and/or sport performance and increased risk of muscle injuries and/or stress fractures was reported. Further investigations are required to determine whether an optimal serum range of vitamin D exists that improves the physical performance and immunological status of the athletes and prevents injuries/infections, respectively. This field of research is dynamic and continually expands the understanding of vitamin D’s diverse roles in this specific category of population.