AIMS: The aim of this study was to evaluate the prevalence, clinical features, and the independent impact of frailty-a geriatric syndrome characterized by the decline of physiological systems-and its components, on prognosis after heart failure (HF) hospitalization. METHODS AND RESULTS: FRAIL-HF is a prospective cohort study including 450 non-dependent patients ≥70 years old hospitalized for HF. Frailty was screened according to the biological phenotype criteria (low physical activity, weight loss, slow walking speed, weak grip strength, and exhaustion). The independent influence of frailty on mortality, functional decline, and readmission risks was calculated adjusted for HF characteristics and co-morbidities. Mean age was 80 ± 6 years; 76% fulfilled frailty criteria. Frail patients were older, more often female, but showed no differences in chronic co-morbidities, LVEF, and NT-proBNP levels. Slow walking speed was the most discriminative component between frail (89.2%) and non-frail patients (26%). Overall, 1-year survival was 89% in the non-frail group and 75% in frail subjects (P = 0.003). After adjusting for age, gender, chronic and acute co-morbidities, NYHA, and NT-proBNP, frail patients showed higher risks for 30-day functional decline [odds ratio (OR) 2.20, 95% confidence interval (CI) 1.19-4.08], 1-year all-cause mortality [hazard ratio (HR) 2.13, 95% CI 1.07-4.23], and 1-year readmission (OR 1.96, 95% CI 1.14-3.34). The association of individual components with 1-year adjusted mortality risk was HR 2.14, 95% CI 1.05-4.39 for low physical activity and HR 1.77, 95% CI 0.95-3.29 for slow walking speed. CONCLUSION: Frailty is highly prevalent even among non-dependent elderly HF patients, and is an independent predictor of early disability, long-term mortality, and readmission. Individual frailty components may be useful for risk prediction.