This study aimed to evaluate the prevalence of hypovitaminosis D and the possible risk factors in Thai athletes. This cross-sectional study was conducted in 96 student athletes (73 males, 23 females) at the Institute of Physical Education Udonthani Thailand. Vitamin D (25(OH)D) deficiency (<20 ng/mL) or insufficiency (20-30 ng/mL) was determined using a standard blood test. The mean±SD age was 20.8±1.4 years. The prevalence of hypovitaminosis D was 42.7% (8.3% for vitamin D deficiency, 34.4% for vitamin D insufficiency). Factors related to hypovitaminosis D included being a female (OR=2.7, 95% CI 1.0-7.0, P=0.04), and sun exposure of 30 min or less per day (OR=3.1, 95% CI 1.2-8.0, P=0.01). However, types of sport, sunscreen application, and consumption of high vitamin D foods were not significantly related to hypovitaminosis D prevalence. The relatively high prevalence of hypovitaminosis D in student athletes suggests these sport athletes (particularly the females) should consider increasing their exposure to vitamin D producing mechanisms.