BACKGROUND: The triglyceride-glucose (TyG) related index, as an emerging indicator of insulin resistance, has been shown to be closely associated with the clinical status (incidence of cardiovascular disease, all-cause mortality, etc.) in patients with MASLD. However, differences in this association among patients with or without type 2 diabetes mellitus (T2DM) have not yet been confirmed. This study aims to address this gap. METHODS: This cross-sectional study included 812 patients with MASLD who visited our hospital from January 2021 to January 2025. Patients were divided into two groups based on the presence or absence of coronary heart disease (CHD). Univariate analysis was performed to compare baseline characteristics between groups. Univariate and multivariate logistic analyses were conducted to assess the associations between various biochemical indices, including TyG, and the risk of CHD. An interaction term between TyG and T2DM was constructed to evaluate the effect modification of diabetes status on this association. The performance of multivariate logistic regression models with and without the inclusion of T2DM was compared. Dose-response relationships between TyG and CHD risk under different T2DM statuses were explored, and receiver operating characteristic (ROC) curves were plotted. RESULTS: TyG showed a significant positive correlation with the risk of CHD (OR = 2.035). T2DM was also significantly positively associated with CHD risk (OR = 2.107). Several biochemical indices, including LDL, TG, ALT, AST, GGT, Scr, and HbA1c, were identified as associated factors for CHD (OR > 1), while HDL and eGFR were protective factors (OR < 1). Interaction analysis indicated that the association between TyG and CHD was significantly stronger in patients with T2DM, with an OR of 3.34, which was substantially higher than the OR of 1.89 observed in patients without T2DM. Restricted cubic spline (RCS) analysis demonstrated a linear relationship between TyG and CHD risk in both patients with and without T2DM. The ROC-derived cut-off value for TyG was 7.992 in patients without T2DM and 9.005 in patients with T2DM; beyond these cut-off values, the risk of CHD increased significantly. CONCLUSION: The TyG index shows a significant positive correlation with the risk of CHD in patients with MASLD, and this correlation is modified by T2DM.