Objective: With respect to liver function and heart failure, 46% of acute decompensated heart failure patients exhibit abnormal liver function. However, there have been no reports of the association between liver function and functional capacity in these patients. Our aim was to clarify the relationship between liver function and functional capacity using the peak oxygen uptake (VO 2 ). Methods: We retrospectively identified 36 heart failure patients who were referred to our rehabilitation laboratory. These patients underwent cardiopulmonary exercise testing (CPX). Furthermore, we investigated the correlations between peak VO 2 , blood measurements [e.g., total bilirubin (T-bil) and brain natriuretic peptide], and echocardiographic parameters. Finally, multivariate regression analysis was performed to investigate the independent variables related to peak VO 2 . Results: The mean peak VO 2 was 10.7±2.9 ml/kg/min. Peak VO 2 during CPX correlated inversely with T-bil [r=-0.379, 95% confidence intervals (CI): −0.654 to −0.014, P=0.043], aspartate transaminase (r=-0.426, 95% CI: −0.685 to −0.07, P=0.021), and peak heart rate (r=0.391, 95% CI: 0.029 to 0.663, P=0.036). The significant independent factors associated with peak VO 2 were treatment with statin (β=-3.19, P=0.015) and T-bil levels (β=-4.27, P=0.002). Conclusion: Our findings demonstrated that liver function may contribute to the functional capacity in heart failure patients.