Background: As the standard treatment of complex CAD, CABG was established. Medical recommendations have adopted prognostic models and are now broadly used to evaluate risk and guide treatment. We applied STS scoring system to patients undergoing CABG to evaluate their predictive performance of early mortality and morbidities. Methods: In the period between septemper 2018 and June 2020, we evaluated 100 patients who underwent CABG at the Kasr AL Ainy hospitals. STS values were calculated for the patients who were fall in the isolated CABG model of the STS risk models using the STS calculator v2.9 available online To represent the discriminative power of the scoring system, the area under the receiver operating characteristic (ROC) curve has been used and the Hosmer-Lemeshow statistics were used to evaluate calibration. Results: STS model showed good discrimination power and good calibration in Hosmer and Lemeshow Test in predicting mortality, morbidity, renal failure, neurological complications, DSW infection and long length of stay. Also it showed bad calibration in predicting prolonged ventilation. However, it could not be assessed for reoperation and short length of stay because there were no events. Conclusion: In the population studied subjected to CABG procedures, the STS scoring system has been well calibrated to be utilized, capable of detecting mortality and most of the results examined.