Undernutrition is very common among patients with heart failure (HF). This study evaluated the prognostic values of three nutritional risk/screening indices among patients with acute HF. We retrospectively calculated scores for 465 patients with acute HF using the Controlling Nutritional Status (CONUT) tool, the Geriatric Nutritional Risk Index (GNRI), and the Mini-Nutritional Assessment Short Form (MNA-SF). The outcomes of interest were the 1-year rate of cardiac events (cardiac-related death or HF-related readmission) and the Barthel index as an index of physical function during hospitalization. The CONUT, GNRI, and MNA-SF scores were significantly correlated, although the proportions of a normal nutritional state varied (CONUT: 18.3%, GNRI: 32.9%, and MNA-SF: 43.9%). Kaplan-Meier estimates revealed that cardiac events were more common among patients with undernutrition based on the CONUT score, and multivariable regression analysis revealed that only the CONUT score independently predicted poor outcomes. Furthermore, changes in the Barthel index during hospitalization were significantly correlated with the CONUT score but not with the GNRI and MNA-SF scores. In receiver operating characteristic analyses, the CONUT score had the most powerful predictive values on both the postdischarge incidence of cardiac events and the decline of physical function during hospitalization compared with the GNRI and the MNA-SF. These results indicate that the CONUT score might provide useful information for predicting poor outcomes in patients with acute HF.