Contemporary heart failure (HF) therapies have not resulted in improved outcomes among patients with HF and preserved left ventricular ejection fraction (LVEF). We sought to evaluate the differential effect of LVEF on long-term mortality after hospitalization for acute decompensated HF in a real-world setting. All-cause mortality at 4 years after hospitalization for HF was assessed by LVEF (categorized as preserved [≥50%], mildly [40% to 49%], moderately [30% to 39%], and severely [<30%] reduced) among 1,620 patients enrolled in the Heart Failure Survey in ISrael. Among the study patients, 30% had preserved LVEF and 20%, 25%, and 25%, had mild, moderate, and severe reductions in LVEF, respectively. Multivariate analysis showed that patients with preserved LVEF had a similar risk of long-term mortality as patients with mild or moderate reduction in LVEF (hazard ratio [HR] 0.92 [p = 0.40] and 1.01 [p = 0.90], respectively) while severely reduced LVEF conferred increased increase rate compared with preserved LVEF (HR 1.20, p = 0.04). Interaction term analysis showed that the risk associated with severely reduced LVEF was evident only among patients ≤75 years (HR 1.49, p = 0.003), whereas among older patients, there was no difference in the risk of long-term mortality between those with preserved versus severely reduced LVEF (HR 1.02 [p = 0.86]; p value for age-by-LVEF interaction = 0.03). In conclusion, patients hospitalized for HF who have preserved LVEF experience similar long-term mortality as patients with mild or moderate reductions in LVEF, whereas severely reduced LVEF remains an independent predictor of long-term mortality in this population. The differential effect of LVEF on long-term mortality is significantly attenuated in the older age group.