Background Red blood cell distribution width (RDW) predicts mortality and morbidity in patients with heart failure and coronary artery disease. However, little is known about the relationship between RDW and other well-known biomarkers such as amino-terminal pro-brain natriuretic peptide (NT-proBNP) and high-sensitive C-reactive protein (hsCRP) in acute myocardial infarction (AMI). We assessed the hypothesis that RDW played an independent role for predicting mortality in patients with AMI. Methods and Results We selected 871 AMI patients (624 males, 63.2짹12.6 years, 411 STEMI) from the Infarction Prognosis Study (IPS) registry. Laboratory markers including RDW were measured at admission and we assessed long-term clinical outcomes. For follow-up period (median 944, IQR 592–1424 days), all-cause mortality was 13.0%. When we divided RDW (13.0짹1.0 %) levels into quartile groups, all-cause mortality was significantly different with the increasing tendency for RDW quartile (7.0% vs. 8.4% vs. 8.7% vs. 27.1%, log rank p<0.001). RDW was significantly correlated with hsCRP (r=0.071, p=0.043) and NT-proBNP (r=0.280, p<0.001) after adjusting for age and body mass index. In Cox-hazards proportion analysis, RDW was an independent prognostic marker for all-cause mortality (HR, 1.33; 95% CI 1.12-1.59; p=0.001) after adjusting for age, hypertension, diabetes, chronic renal failure, body mass index, hemoglobin, creatinine, LDL cholesterol, hsCRP, NT-proBNP and left ventricular ejection fraction. This prognostic power was not affected by anemia Conclusions RDW was associated with long-term all-cause mortality independent of hsCRP and NT-proBNP in patients with AMI. Therefore, a single admission RDW measurement is a simple and inexpensive method which may help assess the long-term risk stratification of patients with AMI.