In patients with acute decompensated heart failure (HF), the association of gender and left ventricular ejection fraction (LVEF) with clinical outcomes has not been fully investigated. The aim of this study was to evaluate gender differences in LVEF and adverse outcomes across the full spectrum of LVEF in patients hospitalized for acute decompensated HF. Of the 4,842 patients enrolled in the Acute Decompensated Heart Failure Syndromes registry, 4,231 patients (2,461 men and 1,770 women) discharged alive after hospitalization for acute decompensated HF were investigated to assess the association of gender and LVEF with the primary end point (all-cause death and readmission for HF). Men or women were divided into 5 groups based on the LVEF at hospital discharge (<30%, 30% to <40%, 40% to <50%, 50% to <60%, and ≥60%). The median follow-up period after discharge was 523 (384 to 791) days. The frequency of the primary end point did not differ between men and women (36.5% vs 38.1%, p = 0.291). After adjustment for multiple comorbidities, male patients with an LVEF <30%, 30% to <40%, 40% to <50%, or 50% to <60% had a significantly higher risk of the primary end point than those with an LVEF ≥60%, indicating an inverse association between LVEF and adverse outcomes. In contrast, the adjusted risk of the primary end point was similar for all 5 LVEF groups of female patients. In conclusions, the association between LVEF and outcomes differs markedly between men and women hospitalized for acute decompensated HF, although event-free survival is similar for both genders.