BACKGROUND: Elevated triglycerides to high-density lipoprotein cholesterol (TG/HDL-C) ratio has been utilised as a predictor of outcomes in patients with adverse cardiometabolic risk profiles. In this study, we examined the prognostic value of elevated TG/HDL-C level in an Australian population of patients with high clinical suspicion of coronary artery disease (CAD) presenting for coronary angiography. METHODS: Follow-up data was collected for 482 patients who underwent coronary angiography in a prospective cohort study. The primary endpoint was all-cause mortality and the secondary endpoint was a major adverse cardiac event (MACE). Patients were stratified into two groups according to their baseline TG/HDL-C ratio, using a TG/HDL-C ratio cut point of 2.5. RESULTS: The mean follow-up period was 5.1 ± 1.2 years, with 49 all-cause deaths. Coronary artery disease on coronary angiography was more prevalent in patients with TG/HDL-C ratio ≥2.5 (83.6% vs. 69.4%, p = 0.03). On the Kaplan-Meier analysis, patients with TG/HDL-C ratio ≥2.5 had worse long-term prognosis (p = 0.04). On multivariate Cox regression adjusting for established cardiovascular risk factors and CAD on coronary angiography, TG/HDL-C ratio ≥2.5 was an independent predictor of long-term all-cause mortality (hazard ratio [HR] 2.10, 95% confidence interval [CI] 1.04-4.20, p = 0.04). On multivariate logistic regression adjusting for known cardiovascular risk factors and CAD on coronary angiography, TG/HDL-C ratio ≥2.5 was strongly associated with an increased risk of long-term MACE (odds ratio [OR] 2.72, 95% CI 1.42-5.20, p = 0.002). CONCLUSIONS: Elevated TG/HDL-C ratio is an independent predictor of long-term all-cause mortality and is strongly associated with an increased risk of MACE.