Introduction: Coronary artery bypass grafting (CABG) remains a cornerstone intervention in the management of progressive coronary artery disease; however, insufficient post-discharge self-care may lead to complications, delayed healing, and hospital readmissions. Telenursing has emerged as a promising strategy for supporting patients during early recovery. This study aimed to evaluate the effect of a structured telenursing educational intervention on patients’ knowledge and self-care management during early follow-up after CABG. Methods: A quasi-experimental study was conducted on 114 patients undergoing first-time elective CABG at Assiut University Heart Hospital. Participants were divided into intervention (n = 57) and control (n = 57) groups. Data were collected using a structured knowledge interview questionnaire and validated self-care management scale. Statistical analyses included paired t-tests, independent t-tests, repeated measures ANOVA, chi-square test, and Pearson correlation analysis. Results: The intervention group demonstrated significant improvement in knowledge and self-care management scores one month after discharge compared to baseline and the control group (p < 0.001). A significant positive correlation was observed between patients’ knowledge and self-care management (r = 0.804, p < 0.001). Conclusions: Telenursing intervention was associated with enhanced patient knowledge and self-care management during the early follow-up after CABG. The integration of structured telenursing follow-up into routine nursing care is recommended to support safe recovery and promote patient independence.