Background: Red cell distribution width (RDW) is discovered to be a novel prognostic marker in patients (pts) with heart failure. We have demonstrated that RDW is well correlated with early mitral inflow velocity to early diastolic mitral annular velocity (E/E���), non-invasive echocardiographic parameter for left ventricular filling pressure (LVFP) which also can be a prognostic marker in pts with acute heart failure (AHF). Then we tested the hypothesis that higher RDW would be associated with higher mortality in pts with AHF. Methods and Results: We analyzed baseline laboratory findings including RDW and N-terminal pro-brain natriuretic peptide (NT-proBNP) and echocardiographic parameters in 250 hospitalized AHF pts (129 males, 65.4 짹 14.2 years old). The primary endpoint was a composite endpoint including cardiovascular mortality or total mortality at 1-year. In our study, mean RDW was 14.6 짹 2.0 %, median NT-proBNP was 5715 (IQR 2451-13706) pg/ml and mean LV ejection fraction (LVEF) was 32.6 짹 14.9 %, respectively. During follow-up period, 29 of the 250 pts (11.6 %) died and 27 of 29 cases were in-hospital mortality (93.1%). The Kaplan-Meier analysis revealed that higher tertile RDW group (>14.8%) had a significantly higher mortality rate compared with lower tertile RDW group (���13.5%) (19.1% vs 6.3%, log-rank: p = 0.023) and both higher RDW and higher NT-proBNP group ( > 5700 pg/mL) had a higher mortality rate compared with either higher RDW or higher NT-proBNP group (20.5% vs 12.0% or 7.1%, log-rank: p = 0.012). A higher RDW was an independent predictor of mortality risk after adjusting age, sex, LVEF, estimated glomerular filtration rate and log NT-proBNP level (hazard ratio : 3.199 95% CI 1.194-8.576, p = 0.011) in Cox proportional hazard analysis. Conclusion: We found that RDW was a novel prognostic marker for 1-year mortality and its prognostic power for predicting mortality was independent of NT-proBNP level and other cardiovascular risk factors in pts with AHF.