Abstract Background Endothelial dysfunction is one of the most important early indicators of atherosclerosis in obstructive sleep apnea (OSA) patients. Endothelial cell specific molecules-1 (ESM-1), which is a novel endothelial dysfunction marker that may be linked to cardiovascular disease. We investigated to assess whether circulating ESM-1 levels are correlated with the presence of coronary artery disease (CAD) in patients with OSA. Methods We performed a cross-sectional study in 228 Chinese OSA subjects, including 185 patients with OSA and 43 controls. The Gensini stenosis scoring system was used to assess the severity of CAD. Circulating ESM-1 levels were measured by Human Magnetic Luminex Screening Assay. The associations between circulating ESM-1 levels and CAD were determined by multivariate logistic regression analysis. The association between ESM-1 levels and Gensini scores was determined by multivariate linear regression analysis. Results CAD patients had significantly higher circulating ESM-1 levels compared with non-CAD patients (1279.01[918.52–1770.71] pg/ml vs 585.46[423.61–812.56] pg/ml, P