This study aimed to investigate the relation between the neutrophil-to-lymphocyte ratio (NLR) and the severity of coronary artery stenosis. A total of 219 patients were included in the study, comprising 51 coronary artery atherosclerosis (CAC) patients, 92 stable angina pectoris (SAP) patients, and 76 acute coronary syndrome (ACS) patients. Based on the results of coronary angiography, all patients were divided into two groups according to the Gensini scores: the low-score group (N = 142) and the high-score group (N = 77). The NLR was computed from the ratio of neutrophils and lymphocytes from the complete blood count. The association between the NLR and severity of coronary artery disease was assessed using correlation analysis and logistic regression. The NLR was higher in ACS patients than in SAP and CAC patients (P < 0.05). In addition, the NLR was higher in the high-score group than in the low-score group (P < 0.05). Correlation analysis showed that the NLR was significantly correlated with the Gensini score. After multivariate analysis, high NLRs were independent predictors of high Gensini scores, together with age and high-density lipoprotein. A cutoff NLR of 2.385 predicted high Gensini scores with a sensitivity and specificity of 64 and 63%, respectively.