Background: Acute myocardial infarction is frequently associated with leukocytosis and elevated neutrophil count. Neutrophilia may occur in response to myocardial necrosis which is a potent acute phase stimulus that is associated with a local and systemic inflammatory response. Objective: The aim of this study was to evaluate the left ventricular systolic function in patients with STsegment elevated myocardial infarction and neutrophilia. Patients and Methods: This prospective study included fifty patients with acute ST-segment elevated myocardial infarction at Cardiology Department, Al-Azhar university Hospitals within the period between January 2016 and June 2018. The patients were divided into two groups: Group (A): Thirty patients with neutrophilia. Group (B): twenty patients without neutrophilia. Results: Patient's ECG in 1st period showed that all patients had positive ECG in both groups while at 2nd and 3 rd periods all patients had negative ECG in both groups with statistically significant differences between 1st period and other period (2nd and 3rd period) where P <0.001 at all. According to neutrophil count there was statistically significant difference between the studied groups in all period where P<0.001 at all period. There was statistically significant difference between the studied groups where P<0.001 at baseline and after 48 hours as regard to EF and FS. There was statistically significant difference between the studied groups according to patients RWMA where P<0.001 at baseline and P= 0.002 after 48 hours. Conclusion: Patients with STEMI associated with neutrophilia are significantly associated with early development of congestive heart failure.