Cardiovascular disease and osteoporosis are thought to share common risk factors, and metabolic syndrome (MS) is composed of major risk factors for cardiovascular disease. This study was performed to investigate the relationships between specific MS components and bone mineral density (BMD). BMD was measured at the femoral neck of Korean men aged 40 years or more (n = 1,780) and postmenopausal women (n = 1,108) using dual-energy X-ray absorptiometry. We identified subjects with MS as defined by two criteria, International Diabetes Federation (IDF) and American Heart Association/National Heart, Lung, and Blood Institute (AHA/NHLBI). Body fat and lean mass were measured via bioimpedance analysis. The prevalence of MS was 19.8% and 7.7% in men and 20.8% and 11.6% in postmenopausal women according to the AHA/NHLBI definition and the IDF definition, respectively. After multivariate adjustment, femoral neck BMD was significantly lower in subjects with MS regardless of diagnostic criteria. BMD decreased as the number of MS components increased (P < 0.001 for trends in both sexes). Among MS components, waist circumference was the most important factor in this negative association. When multiple linear regression models were applied to each 5-kg weight stratum to test for a linear trend, waist circumference and fat mass were negatively associated with BMD and lean mass was positively associated with BMD in men but not in women. MS was associated with a lower BMD in Korean men and postmenopausal women, suggesting that visceral fat may lead to bone loss, especially in men.