Background: Frailty is an issue in patients with heart failure (HF). A Korean version of the frailty scale (K-FRAIL) has been developed. Hypothesis: We aimed to analyze the relationship between the K-FRAIL scale and physical performance in patients with HF. Methods: This study included 142 patients with HF aged ≥65 years from a single center. Muscular fitness was assessed using the handgrip test and knee extensor strength measurement. Aerobic capacity was assessed using the cardiopulmonary exercise test and 6-min walk test (6MWT). Frailty was assessed using the K-FRAIL questionnaire. Results: Peak VO2 and 6MWT scores significantly decreased as frailty worsened, but handgrip and knee extensor strength did not. In the multivariate analysis, peak VO2 (β = −.31; p =.002) and 6MWT score (β = −.38; p <.001) showed significant inverse associations with the K-FRAIL score. Based on the receiver operating characteristic curve analysis, the cut-off values of peak VO2 (hazard ratio, 5.08; p =.023) and 6MWT (hazard ratio, 3.99; p =.020) were independent predictors of frailty. Conclusion: In older patients with HF, physical performance correlates with the degree of frailty. The K-FRAIL scale is correlated with the peak VO2 and 6MWT.