Background <p>Heart failure is a major health challenge requiring long-term management. The current study pursed the goal to discover the relationship between perceived social support with self-efficacy and health-promoting behaviors in patients hospitalized in cardiac care units.</p> Method <p>This cross-sectional analytical study was conducted on 193 patients with heart failure (EF ≤ 35, NYHA class I/II) participating in the study at south of Iran in 2024 using a convenience sampling method. The data were collected with three standard questionnaires: Sullivan Cardiac Self-Efficacy Scale (α = 0.93), Cheraghi’s Multidimensional Scale of Perceived Social Support (MSPSS) (α = 0.87), and Health-Promoting Lifestyle Profile(HPLP-II) (α = 0.86). The data were analyzed via SPSS-26 using descriptive statistics (frequency, mean, and standard deviation) and inferential tests (Pearson).</p> Results <p>As the results divulged, perceived social support was significantly associated with self-efficacy and health-promoting behaviors in heart failure patients (<i>P</i> &lt; 0.001). The highest correlation was reported between emotional support and self-efficacy (<i>r</i> = 0.9) and also between instrumental support and stress management at the dimensional level (<i>r</i> = 0.558).</p> Discussion and&#xa0;conclusion <p>According to the findings, the patients who had higher levels of social support outperformed in disease management and adherence to health behaviors. Social support plays a key role in building up self-efficacy and enhancing health-promoting behaviors in heart failure sufferers. The results highlighted the importance of considering support systems in the treatment and care programs of such patients.</p>