Elevated plasma CT-pro-vasopressin (copeptin) has been described as biomarkers for type 2 diabetes (T2D) and the metabolic syndrome (MetS), which, however, was not confirmed by all studies. Here, we analyzed the association of copeptin with T2D, MetS and MetS components in the population-based KORA F4 study. Plasma copeptin concentrations were analyzed in 1,554 study participants. We used fractional polynomial selection procedures to check for nonlinearity of the associations between copeptin and T2D and HbA1c, respectively. In logistic regression models, we investigated associations between copeptin and T2D, MetS and its components according to IDF criteria. In the fractional polynomial approach, linear models fitted best for copeptin. In multivariable adjusted models, copeptin as a continuous variable was associated with T2D and HbA1c only in men (OR = 1.38 per standard deviation, 95 % CI 1.13-1.70 for T2D). Comparing the top quartile Q4 versus Q1-3, elevated copeptin was associated with T2D (OR 2.70, 95 % CI 1.60-4.59) in men but not in women (OR 0.98, 95 % CI 0.52-1.83). Copeptin was not significantly associated with MetS, central obesity, triglycerides and reduced HDL cholesterol. A significant association with copeptin was observed for hypertension in women (OR 1.59, 95 % CI 1.08-2.33) and glucose dysfunction according to IDF criteria in men (OR 1.63, 95 % CI 1.14-2.34). In the KORA F4 study, copeptin was significantly associated with T2D only in men, whereas hypertension was associated with copeptin in women. No other components of the MetS were related to elevated copeptin.