Purpose: Hemoglobin level is associated with outcomes and complications in ST segment Myocardial Infarction (STEMI) patients. The aim of the study is was to evaluate the correlation between admission Hemoglobin level and the incidence of in hospital complications in patients with STEMI treated with primary Percutaneous Intervention (pPCI). Methodology: This was an observational study recruiting STEMI patients at the National Heart Institute. Admission Hemoglobin level withdrawn and the patients receiving pPCI was followed up during their hospital stay for incidence of complications including new significant arrhythmias, no reflow, stroke, contrast induced nephropathy (CIN). Duration of hospital stay was used as an overall indication of incidence of complication. Patients receiving lytic therapy, parenteral antiplatelet, receiving urgent CABG were excluded from the study. Out of 173 patients presented with STEMI to the National Heart Institute in Egypt and recruited for the study, 106 patients only were included in the study. Findings: Significant correlation between admission Hemoglobin level and incidence of new significant arrhythmias, no reflow and prolonged duration of hospital stay P-value (P <0.009, P <0.000, Prob > chi2 = 0.001) respectively. There was a significant association between hemoglobin level at the time of admission in STEMI patients and incidence of in-hospital complications including different types of arrhythmias, no reflow phenomenon, and prolonged duration of hospital stay. Recommendation: All the precautions should be taken by health care providers with efficient team work to avoid no reflow in anemic and polycythemic patients presenting with STEMI in primary intervention.