Eight Constitution Medicine (ECM) is a Korean constitutional medicine system that classifies people into 8 types: Pulmotonia (PUL), Colonotonia (COL), Renotonia (REN), Vesicotonia (VES), Pancreotonia (PAN), Gastrotonia (GAS), Hepatonia (HEP), and Cholecystonia (CHO). Metabolic syndrome (MS) is a major public health problem worldwide. We assessed the prevalence of and associations between ECM and MS. Cross-sectional convenience sample of 245 adults was used at a medical check-up center in Seoul, South Korea, from 2010 to 2015. Adults were classified into 1 of 8 constitutions by an ECM specialist. MS was diagnosed on the basis of National Cholesterol Education Program Adult Treatment Panel III and Asian Pacific Criteria for abdominal obesity. We also computed the prevalence by percentage and calculated odds ratios (ORs) for MS among 6 constitutions with PUL as the reference.Among 245 adults, 20 (8.2%) were diagnosed with PUL, 43 (17.6%) with COL, 35(14.3%) with REN, 4 (1.6%) with VES, 71 (29.0%) with PAN, 0 (0.0%) with GAS, 54 (22.0%) with HEP, and 18 (7.3%) with CHO. The prevalence of MS in the constitutions was significantly different: CHO, 38.9%; HEP, 35.2%; PAN, 18.3%; COL, 11.6%; PUL, 5.0%; REN, 2.9% (P = .001). We observed higher ORs for HEP and CHO (OR = 13.03, 95% confidence interval [CI] = 1.61-105.70; and OR = 13.19, 95% CI = 1.39-125.46, respectively) than for the other constitutions.People with HEP and CHO constitutions could be at higher risk for MS. Therefore, ECM-based diagnosis may be useful for preventing and managing MS.