Background: Acute coronary syndrome (ACS) is a syndrome that involves multiple forms of myocardial ischemia, as ST-segment elevation myocardial infarction (STEMI), non-ST-segment elevation myocardial infarction (NSTEMI), also unstable angina pectoris (UA). SYNTAX score predicts prognosis in stable coronary artery disease (CAD) and ACS cases. Use of Syntax score II (SS II) shows an increase in ACS prognostic accuracy. Aim: We aim to evaluate the correlation between Interleukin 6 (IL-6) values and CAD severity after PCI in ACS patients. Methods: Our study was done in the cardiology department, Mansoura university from January to March 2023. The study was conducted on 120 patients. In this study, patients suffering from chest pain that were admitted performing coronary angiography were included. Patients being classified into an acute coronary syndrome (ACS) group and chronic coronary syndrome (CCS) group (individuals with diseased vessels exhibiting>50% luminal stenosis). In order to find predictive value of intermediate-high SS or highly SS II, multivariate logistic regression was performed. A ROC curve was utilized to predict the levels of IL-6. Results: For ACS differentiation from SA, IL-6 cutoff value 1.89 has sensitivity of 98.6% and specificity of 92% (P<0.0001). For SS≤ 22, IL-6 cutoff value 3.24 has sensitivity of 89.7% and specificity of 91.7% (P<0.0001). For SS II≤ 25, IL-6 cutoff value 1.92 has sensitivity of 97.1% and specificity of 88.6% (P=0.23). Conclusion: IL-6 concentrations are in direct correlation with the degree of CAD in ACS patients undergoing PCI. Thus, IL-6 levels might be a practical and non-invasive indicator for ACS patients who are at elevated risk.