Complete blood count is the most widely available laboratory datum in the early in-hospital period after ST-elevation myocardial infarction (STEMI). We assessed the clinical utility of the combined use of hemoglobin (Hb) level and neutrophil-to-lymphocyte ratio (N/L) for early risk stratification in patients with STEMI. We analyzed 801 consecutive patients with STEMI treated with primary percutaneous coronary intervention (PCI) within 12 hours of onset of symptoms. Patients with cardiogenic shock or underlying malignancy were excluded, and 739 patients (63 ± 13 years, 74% men) were included in the final analysis. Patients were categorized into 3 groups using the median value of N/L (3.86) and the presence of anemia (Hb <13 mg/dl in men and <12 mg/dl in women); group I had low N/L and no anemia (n = 272), group II had low N/L and anemia, or high N/L and no anemia (n = 331), and group III had high N/L and anemia (n = 136). There were significant differences on clinical outcomes during 6-month follow-up among the 3 groups. Prognostic discriminatory capacity of combined use of Hb level and N/L was also significant in high-risk subgroups such as patients with advanced age, diabetes mellitus, multivessel coronary disease, low ejection fraction, and even in those having higher mortality risk based on Thrombolysis In Myocardial Infarction risk score. In a Cox proportional hazards model, after adjusting for multiple covariates, group III had higher mortality at 6 months (hazard ratio 5.6, 95% confidence interval 1.1 to 27.9, p = 0.036) compared to group I. In conclusion, combined use of Hb level and N/L provides valuable timely information for early risk stratification in patients with STEMI undergoing primary PCI.