Red cell distribution width (RCDW) has not been fully investigated for its prognostic impact in patients with acute heart failure (AHF) with or without the cardiorenal anemia syndrome (CRAS). A total of 978 patients (age 75 ± 14 years, 70% men, 43% with CRAS) hospitalized for AHF were enrolled. During a median follow-up duration of 31 months, 472 subjects (48%) died. The postdischarge mortality was positively associated with the increasing RCDW. After accounting for age, gender, co-morbidities, hemoglobin, renal function, sodium level, and N-terminal probrain natriuretic peptide, RCDW remained an independent predictor of mortality (hazard ratio [HR] and 95% CI for a 1% increase of RCDW: 1.09, 1.00 to 1.17, p = 0.04). In the subgroups of patients with or without CRAS, RCDW was an independent predictor of total mortality for both subgroups (HR 1.05, 95% CI 1.00 to 1.10 and HR 1.11, 95% CI 1.07 to 1.15, respectively). In conclusion, elevated RCDW was independently associated with mortality in patients hospitalized for AHF, with or without CRAS.