Background: Globally, coronary artery disease (CAD) continues to be a major cause of morbidity and death. A straightforward, non-invasive diagnostic method mostly used to identify peripheral artery disease (PAD), the ankle-brachial index (ABI) has drawn interest as a possible indicator of systemic atherosclerosis. Aim: The goal of this study was to evaluate the prognostic usefulness of ABI for CAD severity. Methods: This cross-sectional study was carried out over a six‐month period on a total of 180 patients suspected of having CAD at Cardiology Department - Zagazig University Hospitals. The patients were divided into 3 sub-groups according to pre-test probability into low, intermediate and high. Results: The three pre-test probability groups did not differ statistically significantly in terms of left atrial enlargement (LAE), left ventricular ejection fraction (LVEF <50%), or left ventricular end-diastolic dimension (LVEDD). The SYNTAX score and ABI were shown to be significantly correlated negatively (r = -value, P < 0.001). With a P value <0.001 and an AUC of 0.863, the study of the Receiver Operating Characteristic (ROC) curve showed that ABI strongly predicted the severity of CAD. The optimal cut-off value was ≤0.89, yielding 75.76% sensitivity, 85.19% specificity, a positive predictive value (PPV) of 86.2%, and a negative predictive value (NPV) of 74.2%. Conclusion: The Ankle-Brachial Index can help with risk stratification and is a useful, easy, and non-invasive indicator of the severity of coronary artery disease especially in highrisk patients.