Background: Erectile dysfunction (ED) and coronary artery disease (CAD) frequently coexist, sharing common risk factors and pathophysiological mechanisms. The frontal QRS-T angle (fQRST a), a novel electrocardiographic marker reflecting ventricular depolarization-repolarization heterogeneity, has been linked to adverse cardiac outcomes. However, the combined prognostic value of ED and fQRST a in predicting CAD severity remains unexplored. The aim was to investigate whether the coexistence of ED and widened fQRST a is associated with increased CAD severity, and to evaluate their individual and combined utility in identifying patients with advanced CAD. Methods: This prospective observational study included 236 male patients undergoing first-time coronary angiography for suspected CAD. Patients were stratified into 4 groups based on ED status (International Index of Erectile Function-5 [IIEF-5] <=21) and fQRST a (cutoff: 52.5 derece). Coronary artery disease severity was assessed using the Gensini and SYNT AX scores. Hierarchical regression and correlation analyses were performed to evaluate associations. Results: Erectile dysfunction prevalence was 62.7%, and patients with both ED and high fQRST a exhibited significantly reduced ejection fraction and the highest Gensini and SYNT AX scores (all P < .001). Regression analyses demonstrated that ED (beta = 11.927, P = .009, 95% CI: 2.014-21.839), high fQRST a (beta = 9.906, P = .012, 95% CI: 2.710-22.523), and their interaction (beta = 17.233, P = .028, 95% CI: 1.906-32.560) were independent predictors of higher Gensini scores after full adjustment. Similar results were observed for SYNT AX scores. A moderate inverse correlation was found between IIEF-5 and fQRST a (r = -0.436, P < .001). Conclusion: Erectile dysfunction and widened fQRST a are independently and synergistically associated with more severe CAD. Their coexistence identifies a high-risk subgroup with pronounced angiographic abnormalities.