Neutrophil/lymphocyte ratio (NLR) is the strongest white blood cell predictor of adverse outcomes in stable and unstable coronary artery syndromes. The aim of our study was to explore the utility of NLR in predicting long-term mortality in patients with non-ST-segment elevation myocardial infarction (NSTEMI). Consecutive patients with NSTEMI at Staten Island University Hospital were evaluated for study inclusion. Of the 1,345 patients with NSTEMI admitted from September 2004 to September 2006, 619 qualified for study inclusion. Survival analysis, stratified by NLR tertiles, was used to evaluate the predictive value of average inpatient NLR levels. Four-year vital status was accessed with electronic medical records and Social Security Death Index. Patients in the highest NLR tertile (NLR >4.7) had a higher 4-year mortality rate (29.8% vs 8.4%) compared to those in the lowest tertile (NLR <3, Wilcoxon chi-square 34.64, p <0.0001). After controlling for Global Registry of Acute Coronary Events risk profile scores, average NLR level remained a significant predictor of inpatient and 4-year mortality. Hazard ratios per unit increase of average NLR (log) increased by 1.06 (p = 0.0133) and 1.09 (p = 0.0006), respectively. In conclusion, NLR is an independent predictor of short-term and long-term mortalities in patients with NSTEMI with an average NLR >4.7. We strongly suggest the use of NLR rather than other leukocyte parameters (e.g., total white blood cell count) in risk stratification of the NSTEMI population.