Purpose: This descriptive correlational study aimed to investigate the mediating effects of self-efficacy and social support on the relationship between eHealth literacy and self-care competency in patients undergoing percutaneous coronary intervention.Methods: The participants of this study were 146 patients who underwent multiple percutaneous coronary interventions at the Department of Cardiology at Y General Hospital in Jeollabuk-do, South Korea. Data were collected between September 19, 2022 and February 3, 2023, and analyzed using a parallel multiple mediation model in SPSS/WIN 23.0 and Model 4 of the PROCESS Macro 3.5 program. To determine the statistical significance of the indirect effect, 10,000 bias-corrected bootstrapping with 95% confidence intervals was used.Results: The effect size of the indirect effect of eHealth literacy on self-care competency via self-efficacy was 0.07, which was statistically significant, and the effect size of the indirect effect of eHealth literacy on self-care competency via social support was statistically significant at 0.13. These results verified the mediating effects of self-efficacy and social support.Conclusion: This study is significant in that it confirmed the effects of self-efficacy and social support on the relationship between eHealth literacy and self-care competency. In order to improve self-care competency in patients undergoing percutaneous coronary interventions, it is necessary to provide customized education that can improve eHealth literacy. Furthermore, there is a need for self-efficacy enhancement programs and social support strengthening programs that use various educational and material support systems to help individuals accept and access health information easily.