Background: There is currently no gold standard for assessing frailty syndrome in the elderly population with heart failure. The Cardiovascular Health Study (CHS) is a reference standard for evaluating frailty in elderly individuals with heart failure. Still, it requires a dynamometer and a spacious space, rendering it impractical in daily practice. The INA-FRAIL and Study of Osteoporotic Fractures (SOF) Index can often be easy to use; however, it has not been evaluated for diagnostic performance on elderly patients with heart failure in Indonesia. This study aimed to assess the diagnostic performance of INA-FRAIL and SOF-Index in diagnosing frailty in elderly patients with heart failure. Methods: This cross-sectional study evaluated the diagnostic performances of INA-FRAIL and SOF-Index compared to CHS as the gold standard in this study. The population was heart failure patients aged > 60 at Cipto Mangunkusumo Hospital. Results: Analysis from 81 samples shows the prevalence of frailty based on CHS (35.5%), INA-FRAIL (23.5%), and SOF-Index (8,6%). Diagnostic performance analysis of INA-FRAIL showed a sensitivity of 55,17% (95% CI 35.69–73.55), specificity 94.23% (95% CI 84.05– 98.79), and AUC 0.805 (95% CI 0.698–0.912). Diagnostic performance analysis of SOF showed 20,69% sensitivity (95% CI 7.99 – 39.72), 98.08% specificity (95% CI 89.74 – 99.95), and AUC 0.719 (95% CI 0.595 – 0.843). Conclusion: INA-FRAIL and SOF-Index had a significant association with CHS. The cut-off point of INA-FRAIL ≥1 showed the highest sensitivity, while INA-FRAIL ≥2 showed the highest Youden index. The cut-off point of SOF ≥1 showed the highest sensitivity and the highest Youden index. © 2025, Indonesian Society of Internal Medicine. All rights reserved.