Introduction: Although vitamin D deficiency has a high worldwide prevalence among the general population, very little is known about vitamin status in athletes. Aim: To investigate serum vitamin D (25[OH]D) levels after wintertime in male elite basketball players, and to relate these levels to the dietary intake of vitamin D and calcium. Methods: Subjects were 21 players from the same professional Spanish team. Blood samples to assess 25(OH)D levels were collected after wintertime during the 2008/2009 (April) and 2009/2010 (March) seasons. In addition, athletes completed 4-day dietary records to estimate energy consumption and a food frequency questionnaire to determine dietary vitamin D and calcium intake. Serum 25(OH)D levels were 47.8 ± 21.8 nmol/L, with twelve subjects (57%) being vitamin D deficient (< 50 nmol/L). Results: Vitamin D intake was 139 ± 78 IU/day and calcium intake was 948 ± 419 mg/day. Serum 25(OH)D levels correlated with the daily dietary intake of vitamin D (r = 0.65; P = 0.001) and calcium (r = 0.82; P < 0.001). Conclusion: Professional basketball players are at higher risk of hypovitaminosis D after wintertime. Adequate intake of dietary calcium and vitamin D is required if athletes are to avoid low serum 25(OH)D levels when exposure to sunlight is limited.