Purpose
This study aimed to examine the influence of health literacy and autonomy support on health behavior adherence among patients with premature coronary artery disease (PCAD), defined as onset before age 55 years in males and 65 years in females. Methods: A descriptive, cross-sectional design was employed. Data from 153 patients were collected at a hospital in Seoul, South Korea, between January and March 2023. Statistical analyses included the independent t-test, one-way analysis of variance, Pearson correlation coefficients, and hierarchical multiple regression, conducted using IBM SPSS WIN ver. 27.0. Results: Health literacy (β=.36, p<.001) was the strongest determinant of health behavior adherence. A disease duration of more than one year (β=.17, p=.016) was positively associated with adherence, while male sex (β=–.16, p=.039) and the absence of comorbidities (β=–.17, p=.011) showed significant negative associations. Autonomy support from healthcare providers was not significantly associated with health behavior adherence. Conclusion: Healthcare professionals should prioritize improving patient health literacy through tailored communication and educational strategies. Male patients and those newly diagnosed should be recognized as vulnerable groups for low adherence. Targeted interventions should be designed to meet their specific needs. Furthermore, patients with PCAD should be guided to increase their awareness and understanding of their condition.