© 2021 Limited Liability Company KlinMed Consulting. All rights reserved.Goal In this study, it was investigated whether the age, creatinine, and ejection fraction (ACEF) score [age (years)/ejection fraction (%) +1 (if creatinine >2 mg/dL)] could predict in-hospital mortality in patients with non-ST-elevation acute coronary syndrome (NSTE-ACS) and its relationship with the Global Record of Acute Coronary Events (GRACE) risk score were investigated. Material and methods The study enrolled 658 NSTE-ACS patients from January 2016 to August 2020. The patients were divided into two groups according to the ACEF score with an optimum cut-off value of 1.283 who were divided into two groups according to the ACEF score: low ACEF (≤1.283, n:382) and high ACEF (>1.283, n: 276). The primary outcome of the study was in-hospital all-cause mortality. The primary outcome of the study was in-hospital all-cause mortality. Statistically accuracy was defined with area under the curve by receiver-operating characteristic curve analysis. Results In total, 13 (4.71%) patients had in-hospital mortality. The ACEF score was significantly higher in the group with higher mortality than in the group with low mortality (2.1±0.53 vs. 1.34±0.56 p=0.001). The ACEF score was positively correlated with GRACE risk score (r=0.188 p<0.0001). In ROC curve analysis, the AUC of the ACEF score for predicting in-hospital mortality was 0.849 (95% CI, 0.820 to 0.876; p<0.0001); sensitivity, 92.3%; specificity, 59.2%, and the optimum cut-off value was >1.283. Conclusion The ACEF score presented excellent discrimination in predicting in-hospital mortality. We obtained an easier and more useful result by dividing the ACEF score into two groups instead of three in NSTE-ACS patients. As a simple, useful, and easily applicable risk stratification in the evaluation of an emergency event such as the ACEF score, it can significantly contribute to the identification of patients at high risk.