Background <p>This study aimed to examine the knowledge, attitudes, and practices (KAP) related to cardiac rehabilitation (CR) among patients with heart failure (HF).</p> Methods <p>A cross-sectional study was conducted among 589 patients with HF at the Affiliated Hospital of Guizhou Medical University from August 31, 2025 to November 18, 2025. Demographic information and KAP scores were obtained using a self-designed questionnaire. Structural equation modeling (SEM) was applied to assess the associations among the KAP components.</p> Results <p>A total of 589 valid questionnaires were included in the analysis, yielding an effective response rate of 88.57%. Of the participants, 306 (51.95%) were male, and the mean age was 49.89 ± 14.30 years. The mean scores for knowledge, attitude, and practice were 6.48 ± 2.50 (range: 0–11), 29.36 ± 4.50 (range: 8–40), and 28.18 ± 7.35 (range: 8–40), respectively. SEM analysis indicated that knowledge had a direct positive effect on attitude (β = 0.87, <i>P</i> &lt; 0.001) and a direct negative effect on practice (β = −1.06, <i>P</i> &lt; 0.001), whereas attitude showed a direct positive effect on practice (β = 0.78, <i>P</i> &lt; 0.001). Moreover, knowledge exerted a positive indirect effect on practice through attitude (β = 0.68, <i>P</i> = 0.001).</p> Conclusion <p>Patients with HF demonstrated moderate knowledge levels, generally positive attitudes, and relatively active practices regarding cardiac rehabilitation. The findings indicate that the association between knowledge and practice is not linear, with attitudes serving as an important mediating factor. These results suggest that efforts to enhance participation in cardiac rehabilitation should focus not only on improving patient knowledge but also on addressing attitudinal and contextual influences that affect the translation of knowledge into practice.</p>