Background: The aim of primary percutaneous coronary intervention (pPCI) in acute STEMI is to restore the blood flow within the infarct-related artery, leading to improvement of survival and quality of life of the patient. Objective: It was to assess the in-hospital outcomes of pPCI in relation to left ventricular ejection fraction (LVEF). Patients and Methods: The study was observational cross-sectional. It included 270 patients who had undergone pPCI in the period between May 2018 and May 2019 at Assiut University Heart Hospital. Results: Patients were divided according to LVEF into three groups; group I: 28 (10.4%) with LVEF <25%, group II: 150 (55.6%) with LVEF 25-50%, and group III: 92 (34.1%) with LVEF >50%. In-hospital complications; in group I: 17 patients (60.7%), 8 patients developed pulmonary edema, 7 patients with cardiogenic shock and 2 patients with ventricular tachycardia (VT). In group II: 22 patients (14.7%), 10 patients with pulmonary edema, 4 patients with cardiogenic shock and each of VT, complete heart block, re-infarction and stent thrombosis occurred in two patients. In group III: only 4 patients (4.4%), 2 patients with atrial fibrillation and 2 patients with complete heart block. Conclusion: LVEF is an important predictor of clinical outcomes in STEMI patients. Reduced LVEF is a risk factor for in-hospital mortality in those patients after pPCI. Other predictors include age (>70 years), pulmonary edema, and SBP less than 100 mmHg. Awareness of these predictors may assist clinicians to make better clinical decisions for STEMI patients.