Objectives: In this study, we aimed to investigate the relationship between neutrophil to lymphocyte ratio (NLR) and infarct-related artery (IRA) patency in patients with ST-segment elevation myocardial infarction (STEMI).Methods: A total of 349 patients with STEMI were recruited to this retrospective study. Baseline characteristics were reviewed. Patency of IRA was evaluated by thrombolysis in myocardial infarction flow grade.Results: Of all patients, 293 patients formed the occluded IRA group and 56 patients formed the patent IRA group. The NLR was significantly higher in occluded IRA group (4.4 ± 4.1 vs 1.9 ± 1.1, P < .001). Glucose levels were also higher in occluded IRA group (171.3 ± 78.0 vs 144.7 ± 49.7, P = .022). Regression analysis demonstrated admission NLR and plasma glucose levels as independent predictors of IRA patency.Conclusion: In this study, we found that admission NLR and glucose levels were higher in patients with occluded IRA than in patients with STEMI. We also found that NLR and glucose levels were independent predictors of IRA patency. Because hemogram is a cheap, fast, and widely available test, it can be used in daily practice as a predictor of IRA patency.