Malnutrition is common in patients with heart failure with reduced ejection fraction (HFrEF) and may influence the long-term prognosis and allocation of combination medical therapy. We reviewed 1231 consecutive patient-level records from a multicenter Japanese registry of hospitalized HFrEF patients. Nutritional status was assessed using geriatric nutritional risk index (GNRI). Combination medical therapy were categorized based on the use of beta-blockers, renin-angiotensin system inhibitors, and mineralocorticoid receptor antagonists. The composite outcome of all-cause death and HF rehospitalization was assessed. The mean age was 72.0 ± 14.2 years and 42.6% patients were malnourished (GNRI < 92). At discharge, 43.6% and 33.4% of patients were receiving two and three agents, respectively. Malnourished patients had lower rates of combination medical therapy use. The standardized GNRI score was independently associated with the occurrence of adverse events (hazard ratio [HR]: 0.88, 95% confidence interval [CI] 0.79–0.98). Regardless of the GNRI score, referenced to patients receiving single agent, risk of adverse events were lower with those receiving three (HR: 0.70, 95% CI 0.55–0.91) or two agents (HR: 0.70, 95% CI 0.56–0.89). Malnutrition assessed by GNRI score predicts long-term adverse outcomes among hospitalized HFrEF patients. However, its prognosis may be modified with combination medical therapy.