Background. It remains uncertain whether the metabolic syndrome (MS) or insulin resistance contribute to the association between vitamin D deficiency and obesity. Methods. We conducted a cross-sectional survey of 343 subjects who were overweight or obese. We analyzed anthropometric data and the presence or absence of MS. Additionally, we determined 25-hydroxyvitamin D (25OHD) and insulin concentrations, and the HOMA index was calculated. Chi-square test,Mann-Whitney U test, Student's t-tests,and logistic regression analysis were used. Results. The mean age of the patients was 42 ± 11 years, and 65.9% were women. The mean BMI was 34.7 ± 8.3 kg/m(2) and 25(OH)D levels were 53.7 ± 29.8 nmol/L. Forty-six patients (13.4%) had MS. Vitamin D status was associated with the degree of obesity, especially with a BMI > 40 kg/m(2). Patients with MS had lower levels of 25(OH)D than patients without (43.3 ± 29.0 versus 55.3 ± 29.6 mmol/L, resp.), and the odds ratio for hypovitaminosis D was 2.7 (confidence interval (CI), 1.14-6.4) (P = .023) for patients with MS versus patients without MS, irrespective of the degree of obesity. Conclusions. Our data confirm the association between vitamin D and MS and suggest that this association is independent of the degree of obesity.