Heart failure (HF) can cause metabolic imbalances, leading to anabolic resistance and increased energy expenditure, which often results in weight loss and cachexia. Comprehensive cardiac rehabilitation (CR), including exercise, nutritional support, and risk management, is crucial for enhancing the health and quality of life of patients with HF and is expected to play a central role in the prevention and treatment of HF-associated cachexia. However, the prevalence of cachexia in patients with HF undergoing comprehensive outpatient CR is currently unknown, and the detailed characteristics including of motor function of such patients remain undefined. Therefore, this cross-sectional study aimed to investigate the prevalence and characteristics of cachexia and the relationship between cachexia and lower limb motor function in patients with HF undergoing outpatient CR. This study included 115 consecutive patients with HF (43% male; mean age, 78 ± 8 years) who underwent comprehensive outpatient CR. The cachexia status was assessed according to the definition proposed by the Asian Working Group on Cachexia in 2023. The Short Physical Performance Battery (SPPB) and Mini Nutritional Assessment Short-Form (MNA-SF) were used to evaluate motor function of the lower limbs and nutritional status, respectively. Multivariate logistic regression analyses were used to examine the potential relationship between cachexia and low SPPB scores (≤ 9 points). The prevalence of cachexia was 30% in this study. Compared with those without cachexia, patients with cachexia were significantly older and showed notable reductions in body mass index, MNA-SF scores, handgrip strength, gait speed, and SPPB scores. A multivariate logistic regression analysis, adjusted for confounders, revealed that both age (odds ratio [OR], 1.129; 95% confidence interval [CI], 1.034-1.248; P = 0.016) and presence of cachexia (OR, 3.783; 95% CI, 1.213-11.796; P = 0.022) were independently associated with low SPPB scores. These findings highlight the importance of focusing on cachexia in patients with HF as part of a comprehensive outpatient CR and may be crucial in developing treatments to improve lower limb motor function in patients with HF who develops cachexia.