Background <p>Chronic obstructive pulmonary disease (COPD) and coronary heart disease (CHD) frequently coexist. This study aims to investigate the potential association between the triglyceride-to-high-density lipoprotein ratio (THR) and the risk of CHD in patients with COPD.</p> Methods <p>In this study, we investigated the association between the THR and CHD among patients with COPD using two representative cohorts: the U.S. National Health and Nutrition Examination Survey (NHANES) and a Chinese cohort. Logistic regression models were applied to assess the relationship between THR and CHD in patients with COPD. Restricted cubic spline (RCS) analysis was conducted to explore potential linear associations. Additionally, subgroup analyses were performed to identify population-specific differences.</p> Results <p>This study included 253 American participants and 404 Chinese participants. In both the U.S. NHANES cohort and the Chinese cohort, each unit increase in THR was associated with a significantly lower likelihood of CHD in COPD patients(NHANES: OR = 0.682, 95% CI: 0.466–0.998, <i>P</i> = 0.049; China: OR = 0.688, 95% CI: 0.521–0.908, <i>P</i> = 0.008). RCS analysis demonstrated linear associations in both the NHANES cohort (<i>P</i> = 0.027, <i>P</i> for nonlinearity = 0.449) and the Chinese cohort (<i>P</i> = 0.023, <i>P</i> for nonlinearity = 0.374). Subgroup analysis further indicated that age ≥ 60 years significantly modified the association between THR and CHD in patients with COPD (OR = 0.509, 95% CI: 0.347–0.745, <i>P</i> &lt; 0.001).</p> Conclusion <p>This study demonstrates a significant association between the THR and CHD in middle-aged and elderly patients with COPD; however, the focus on this population may introduce selection bias. Future studies should validate these findings through well-designed longitudinal investigations to improve the robustness and generalizability of the results.</p>