There is little data regarding the diagnostic ability of neutrophil-lymphocyte ratio (NLR) in acute coronary syndrome. Therefore, we aimed to assess the predictive value of NLR in the discrimination of troponin-positive patients. We enrolled 244 patients (mean age 61.3 ± 11.7 years, 70.5% male) who presented to the emergency service with acute chest pain. Patients were divided into 2 groups based upon the troponin positivity in the 12- to 24-hour follow-up. The admission NLR was significantly higher in the troponin-positive group (5.49 ± 4.01 vs 2.40 ± 1.36, P <.001). A cutoff point of 2.80 for NLR measured on admission had 79% sensitivity and 73% specificity in predicting follow-up troponin positivity. After multivariate analysis, admission NLR and glucose levels remained significant predictors of follow-up troponin positivity. In conclusion, NLR may be an early diagnostic marker in emergency service for discriminating patients who will have a positive troponin test in the follow-up.