In this study we aimed to investigate whether there is an association between the neutrophil to lymphocyte ratio (NLR) and severity of coronary artery disease (CAD) in patients with non-ST segment elevation myocardial infarction (NSTEMI) using the SYNTAX score (SXscore). A total of 414 patients with NSTEMI who underwent coronary angiography were enrolled in the study. NLR was measured for all patients at presentation. The study population was then divided into 3 tertiles based on the SYNTAX trial results.(1)) The low syntax group (n = 329) was defined as those with an SXscore ≤ 22, the intermediate syntax group (n = 58) was defined as an SXscore ≥ 23 and < 33, and the high syntax group (n = 27) as those with an SXscore ≥ 33. NLR was significantly lower in patients with a low SXscore compared to patients with an intermediate SXscore or high SXscore (3.7 ± 4 to 4.6 ± 2 and 7.9 ± 4, P < 0.001). Linear regression analysis revealed that NLR (coefficientβ = 0.380, 95%CI: 1.165-1.917, P < 0.001) was significantly associated with the SXscore in patients with NSTEMI. Our results indicate that NLR is independently associated with the severity of CAD in patients with NSTEMI.