Background: ST elevation myocardial infarction (STEMI) is a clinical syndrome defined by characteristic symptoms of myocardial ischemia accompanied by persistent elevation the ST segment on electrocardiograph (ECG) and subsequent release of biomarkers of myocardial necrosis. Objective: The aim of the study was to evaluate the possibility of usefulness of CHA2DS2 -VASc Score as a predictor of short-term complications in STEMI patients without atrial fibrillation. Patients and methods: This prospective cohort study was carried out on 80 STEMI patients who presented to the Coronary Care Unit (CCU), Zagazig University Hospital, during the period from December 2021 to June 2022. They were divided into two equal groups: Group (A); STEMI without AF, included 40 patients, 31 (77.5%) males and 9 (22.5%) females whose age ranged from 35 to 75 years. Group (B); STEMI with AF, included 40 patients, 28 (70%) males and 12 (30%) females whose age ranged from 42 to 78 years. CHA2DS2- VASc Score, and syntax score were calculated for each patient. Results: The average EF% among STEMI patients without AF was higher than STEMI patients with AF (53.5 ± 7.5> 49.4 ± 10.5) ranged from (36 to 66) and from (33 to 68) respectively, this difference was statistically significant (p-value=<0.04*). CHA2DS2-VASC score with cutoff value ≥ 4 was very good predictor for high syntax score in both groups. Conclusion: It could be concluded that CHA2DS2-VASc score could be applied to predict the risk of subsequent thromboembolic events in patient with atrial fibrillation. This score has represented ample power in estimating major adverse cardiovascular outcomes in the sitting of acute coronary syndrome.