Vitamin D is pivotal for bone health, muscle strength, recovery, and overall athletic performance. This article discusses the effects of Vitamin D deficiency among athletes, with a specific focus on its connection to sports-related conditions like Relative Energy Deficiency in Sport (RED-S) and Juvenile Osteochondritis Dissecans (JOCD). Additionally, we review the importance of vitamin D for muscle strength and muscle repair. Vitamin D deficiency exacerbates the risk of stress fractures in RED-S patients due to its impact on bone biology. Research points to an increased incidence of vitamin D deficiency in JOCD patients, indicating a potential connection between the condition and low Vitamin D levels. Children and athletes should be screened for vitamin D deficiency as supplementation has been found to have positive outcomes. This article underscores the pivotal role of Vitamin D in athletic performance. Further research is essential to elucidate how Vitamin D deficiency contributes to sports-related pathologies and to establish the optimal Vitamin D levels for injury prevention in athletes.