Background: Hospitalization often leads to a decline in activities of daily living (ADL) in older patients with heart failure. Although cardiac rehabilitation (CR) improves ADL, it can be difficult to perform CR due to the deconditioning of these patients. This study aimed to examine the factors associated with ADL at discharge in older patients with heart failure who underwent CR. Methods: A total of 86 of 110 older heart failure patients aged ≥ 75 years (average age, 86.9 ± 5.7 years) transferred to our institution for CR were enrolled and classified into high ADL at discharge (n = 54) and low ADL at discharge (n = 32) groups. Physical characteristics, comorbidities, medications, blood test data, echocardiographic data, and nutritional status (Geriatric Nutritional Risk Index [GNRI]) were retrospectively examined from medical records. ADL were assessed using the Barthel Index (BI) at admission and discharge. Considering multicollinearity, the relationship between high ADL (BI ≥ 60) at discharge and these assessments at admission was analyzed using multiple logistic regression analysis. The receiver operating characteristic curve was analyzed to calculate the cutoff values for the parameters identified by the multiple logistic regression analysis. Results: The GNRI was the only independent factor predicting high ADL at discharge (p = 0.041; odds ratio [OR], 1.125; 95% confidence interval [CI], 1.005–1.260). The area under the receiver operating characteristic curve for the GNRI was 0.770 (95% CI, 0.664–0.876). The cutoff value for the GNRI was 83.4 (sensitivity, 85.2%; specificity, 62.5%). Conclusion: These findings suggest that the GNRI score at admission predicts high ADL at discharge in older patients with heart failure who underwent CR.