INTRODUCTION: Estimating the mortality rate of patients after cardiac surgery is an important issue in clinical practice. The age, creatinine, and ejection fraction (ACEF) score is one of those scoring models developed for this purpose.We aimed to validate themortality scoringmodel,ACEF II (age, creatinine, ejection fraction, hematocrit, and emergency of the surgery), in the patient population undergoing isolated coronary artery bypass grafting surgery. METHODS: Patients with coronary artery disease who underwent isolated coronary artery bypass grafting were retrospectively analysed. Data from January 2022 to December 2022 are included. ACEF II scoring model points were calculated. The efficacy of this model in predicting 30-day mortality was determined by the receiver operating characteristic (ROC) curve. RESULTS: 429 patients were included in the analysis. One-month mortality was 6.1% (n = 26). There was a statistically significant difference in terms of age, ejection fraction, heart failure, creatinine, hematocrit, ACEF scores, status of operation (elective/emergency), and cardiopulmonary bypass time. (p = 0.001; p < 0.01). The cut-off value of the ACEF II score and area under the ROC curve were, respectively, 4.2 and 0.992. The risk of mortality in cases with an ACEF II score above 4.2 was found to be 2.238 (95% CI: 1.628-3.076) times higher. In multivariate Logistic regression analysis, ACEF II Score and heart failure were significant risk factors (p < 0.05). CONCLUSIONS: We concluded that the ACEF II score and heart failure were independent risk factors for mortality. ACEF II has a good ability to discriminate for predicting mortality in the cardiac surgical population.