Recent studies have suggested that low levels of 25-hydroxyvitamin D (25OHD) are associated with cardiovascular risks in medical patients. However, these associations have not been well documented in high risk surgical patients. We hypothesized that serum 25OHD, 1,25-dihydroxyvitamin D (1,25OHD) would be associated with the cardiac operative risk stratification score. The study was conducted with a cross-sectional design at a single academic medical center in Japan. Two hundred five adult patients scheduled for major cardiovascular surgery were included consecutively. Cardiac operative risk was evaluated with the European System for Cardiac Operative Risk Evaluation (EuroSCORE) scoring system. Correlations between 25OHD and 1,25OHD, and EuroSCORE were assessed using simple and multiple linear regression models. Mean 25OHD and 1,25OHD were 20.1 ± 7.1 ng/mL and 51.2 ± 19.2 pg/mL, respectively. Half and 88% of the study population showed deficient (<20 ng/mL) and insufficient (<30 ng/mL) 25OHD levels, respectively. In contrast, only 3% showed 1,25OHD levels lower than normal (<20 pg/mL). Circulating 25OHD levels, but not 1,25OHD levels, were negatively correlated with EuroSCORE (p=0.005) even after adjusted for body mass index, albumin, hypertension, dyslipidemia, diabetes mellitus, creatinine, use of statin, high sensitive C-reactive protein, and intact parathyroid hormone. These results suggest that serum 25OHD levels are inversely associated with operative risk severity of patients undergoing major cardiovascular surgery.