Background: Elevated N-terminal pro-B-type natriuretic peptide (NT-proBNP) is associated with clinically overt heart failure (HF). Whether it provides additive prognostic information for incident HF beyond traditional HF risk factors and left ventricular (LV) mass index has not been evaluated. Objective: We studied the association of plasma NT-proBNP over and above that of magnetic resonance imaging (MRI) defined LV mass for incident HF in an asymptomatic multiethnic population. Methods: 5597 multiethnic participants without clinically-apparent cardiovascular disease who had NT-proBNP measured at baseline were followed for 5.5 짹 1.1 years. Among them 4163 had cardiac MRI at baseline. Results: During follow-up 111 participants experienced incident HF. Higher NT-proBNP was significantly associated with incident HF, independent of baseline age, sex, ethnicity, systolic blood pressure, diabetes, smoking, estimated glomerular filtration rate, medications (anti-hypertensive and statin), LV mass index and interim myocardial infarction [HR 1.95 per 1 unit (pg/ml) log NT-proBNP increment, 95% CI 1.54-2.46, p<0.001]. This relationship held among three ethnic groups, non-Hispanic whites, African Americans and Hispanics. Most importantly, NT-proBNP provided additive value beyond both traditional risk factors and LV mass index for predicting incident HF [C-index 0.89 vs. 0.85, p=0.01; integrated discrimination index=0.046, p<0.001; net reclassification index (NRI; 6-year risk probability categorized by <3%, 3-10%, >10%) =0.175, p=0.019; category-less NRI=0.561, p<0.001]. Conclusions: Plasma NT-proBNP provides prognostic value beyond traditional risk factors and MRI determined LV mass index for incident symptomatic HF in an asymptomatic multiethnic population.