Background: Cardiac fibrosis is common and associated with poor prognosis in patients with heart failure. We investigated the effect of cardiac fibrosis on the left ventricular (LV) diastolic function, functional capacity, LV remodeling, and biochemical parameters in patients with nonischemic dilated cardiomyopathy (NIDC). In addition, we investigated the biochemical and echocardiographic predictors of cardiac fibrosis in this group. Methods and Results: Forty patients with NIDC were enrolled. Cardiac fibrosis was evaluated according to the presence of late gadolinium enhancement (LGE) on cardiac magnetic resonance (CMR) imaging. Nineteen patients had cardiac fibrosis (Group I) and 21 patients did not have cardiac fibrosis (Group II). LV systolic and diastolic parameters were assessed with conventional and tissue Doppler echocardiography. N-terminal pro-B-type natriuretic peptide (NT-pro BNP) levels of each patient were recorded. Patients with cardiac fibrosis had impaired diastolic function, higher functional class and NT-pro BNP levels, and significant LV remodeling than the patients without cardiac fibrosis. A correlation analysis revealed that the cardiac fibrosis severity was associated with functional class, cardiac chamber sizes, NT-pro BNP levels, diastolic parameters such as E/Se. A linear regression analysis demonstrated that NT-pro BNP and E/Se were the independent predictors of cardiac fibrosis. Conclusion: Cardiac fibrosis correlates with impaired LV diastolic function and functional capacity, elevated NT-proBNP levels, and adverse cardiac remodeling in patients with NIDC. Therefore, the assessment of cardiac fibrosis can be useful in the management of these patients. (Echocardiography 2010;27:954-960).