AIMS: Cardiovascular hospitalization (CVH) in patients with heart failure (HF) is associated with a high post-discharge rate of early re-admission and CV death. Eplerenone might be effective in reducing the incidence of these adverse clinical outcomes during this period. METHODS AND RESULTS: The EMPHASIS-HF trial compared eplerenone with placebo added to standard therapy in 2737 patients with New York Heart Association class II HF and left ventricular ejection fraction ≤35%. We conducted a post hoc analysis in the 2338 patients randomized within 180 days of a CVH. The interaction between the time from the qualifying CVH to randomization and the primary outcome of CV death or hospitalization for HF (HHF), as well as other secondary outcomes, was assessed in Cox survival models. Most of the qualifying CVHs were HHF (N = 1496, 64.0%), acute coronary syndromes (N = 390, 16.7%), and arrhythmias (N = 197, 7.2%). The median time of study drug initiation from qualifying CVH was 42 days. The relative rate reductions in CV death/HHF, HHF, and all-cause mortality were similar (P for interaction = 0.65, 0.44, and 0.40, respectively) whether the treatment was initiated <42 or 42+ days after qualifying CVH. Absolute rate reductions were -5.61 [-8.67, -2.55] events per 100 patient × years in the <42 days group and -3.58 [-6.37, -0.79] in the 42+ days group. The adverse effects of eplerenone were also unaffected by the time from the qualifying CVH. CONCLUSION: Eplerenone is safe, improves survival, and may prevent re-admission when initiated soon after a hospitalization for HF or acute coronary syndromes in patients with systolic HF and mild symptoms.