The platelet to lymphocyte ratio (PLR) has recently emerged as a potential inflammatory biomarker. Hence, we assessed the relationship between PLR and the extent/severity of coronary artery disease (CAD) using the Gensini score in association with the inflammatory marker C-reactive protein (CRP) in patients with stable CAD. Angiographic data of 1646 patients were analyzed in this cross-sectional study. Patients were categorized according to Gensini scores as no CAD (control), mild, and severe CAD groups. The PLR in the control group was significantly lower than those of mild and severe CAD groups. In multivariate logistic regression analysis, PLR was found to be an independent predictor of the presence of severe CAD (odds ratio: 1.043 [1.036-1.049], P < .001). Furthermore, there was a significant correlation between PLR and the severity of CAD (r = .370, P < .001) and CRP levels (r = .312, P < .001). In conclusion, PLR was independently and positively associated with the severity of coronary atherosclerosis. These results suggest that PLR is an easily available and cheap inflammatory indicator that can be used in predicting the severity of CAD.