INTRODUCTION: The anemia leads to a worse prognosis in patients with heart failure(HF). There are few data on the impact of anemia on mortality in patients with acute heart failiure(AHF), and the studies available are mainly retrospective and include hospitalized patients. OBJECTIVE. Evaluate the role of anemia in 30-days and one-year mortality in patients with AHF attended in hospital emergency departments(HEDs). METHODS. Multicenter, observational study of prospective cohorts of patients with AHF. Study variables: anemia(hemoglobin<12g/dL in women and <13g/dL in men), 30-days-mortality and at one year, risk factors, comorbidity, functional impairment, basal functional grade for dyspnea, chronic and acute treatment, clinical and analytical data of the episode and patient destination. Statistical analysis: bivariate analysis and survival analyses using Cox regression. RESULTS. A total of 13,454 patients were included, 7662(56.9%) of whom had anemia. Those with anemia were older, had more comorbidity, a worse functional status and New York Heart Association class, greater renal function impairment and more hyponatremia. The mortality was higher in patients with anemia at 30-days and one-year: 7.5% vs. 10.7%(p<0.001) and 21.2% vs. 31.4%(p<0.001), respectively. The crude and adjusted hazard ratios of anemia for 30-days-mortality were: 1.46(confidence interval[CI]95% 1.30-1.64);p<0.001 and 1.20(CI95% 1.05-1.38);p=0.009, respectively, and 1.57(CI95% 1.47-1.68) and 1.30(CI95% 1.20-1.40) for one-year-mortality. The weight of anemia on mortality was different in each follow-up period. CONCLUSIONS. Anemia is an independent predictor of 30-days-mortality and one year in patients with AHF attended in HEDs. It is important to study the etiology of AHF since adequate treatment would reduce mortality.