Background. Recent evidence demonstrated that the circulating levels of omentin-1 are related to the presence of ischemic heart disease and heart failure. However, omentin-1 plasma levels in patients with nonischemic dilated cardiomyopathy (DCM), which is the most common etiology of heart failure, have yet to be investigated. Methods. Plasma levels of omentin-1 and adiponectin were measured in 100 patients with DCM and 45 healthy controls. Results. Plasma omentin-1 levels significantly decreased in DCM patients compared with the control group, whereas adiponectin levels significantly increased in DCM patients compared with the control group. Plasma omentin-1 levels were negatively correlated with adiponectin (R = -0.376, P = 0.005), C-reactive protein (CRP) (R = -0.320, P = 0.001), and N-terminal pro-brain natriuretic peptide (NT-proBNP) (R = -0.365, P = 0.000) levels as well as left ventricular end-diastolic diameter (LVEDD) (R = -0.200, P = 0.046) but were positively correlated with left ventricular ejection fraction (LVEF) (R = 0.496, P = 0.000). Plasma adiponectin levels were positively correlated with CRP (R = 0.273, P = 0.006) and NT-proBNP (R = 0.329, P = 0.001) levels but were negatively correlated with fasting glucose (R = -0.218, P = 0.029) and LVEF (R = -0.615, P = 0.000) levels. Furthermore, omentin-1 (OR 0.983, 95% CI 0.970 to 0.996; P = 0.008) levels were independently associated with the presence of DCM before NT-proBNP was added. Conclusions. Omentin-1 is a novel biomarker of DCM.