Objective We assessed the correlation between serum carbohydrate antigen 125 (CA125) and carotid intima-media thickness (cIMT) in patients with coronary artery disease (CAD). Methods We collected 518 CAD patients from the cardiovascular disease center in our hospital, and all cIMT values were measured in patients with CAD. Results The serum CA125 concentrations were found to be increased in CAD patients with early carotid atherosclerosis compared with patients without early carotid atherosclerosis (20.1±7.72 vs. 17.7±6.41 U/mL, p<0.001). The cIMT values were increased in patients with higher serum CA-125 levels than those with lower serum CA-125 concentrations (1.16±0.32 vs. 0.98±0.29 mm, p<0.001). There was a positive correlation between serum CA125 and cIMT in CAD patients (r=0.262, p<0.001). Moreover, the serum CA125 concentrations also were positively correlated with cIMT in subjects with early carotid atherosclerosis and without early carotid atherosclerosis (r=0.255, p<0.001; r=0.189, p=0.002). We found that serum CA-125 concentrations were independently correlated with cIMT (beta = 0.293, p<0.001) in multiple linear regression analysis. Conclusions We found that serum CA125 concentrations were positively correlated with cIMT in CAD patients, serum CA125 might be a potential biochemical marker for the estimation of atherosclerosis in patients with CAD.