Objective: This study aimed to evaluate the effectiveness of the CRB-65 score as a prognostic predictor in acute heart failure (HF) patients who visited the emergency department (ED). Methods: This study was performed retrospectively on HF patients over the age of 19 years admitted to the ED between August 2018 and July 2020. The patients who met the Framingham criteria, including acute pulmonary edema, were classified by the CRB-65 score and compared with previous HF prognostic predictors (Acute Decompensated Heart Failure National Registry, Get with The Guidelines-Heart Failure and Enhanced Feedback for Effective Cardiac Treatment). We defined the primary outcome as 30-day mortality and secondary outcomes as hospitalization days (HD), admission to intensive care unit (ICU), length of stay (LOS) in the ICU and mechanical ventilation (MV). We conducted linear regression and logistic regression with these outcomes and obtained the area under the receiver-operating characteristics (AUROC) curve to compare the predictive power of the primary outcome. Results: A total of 462 patients were included in the study, and their mean age was 80 years. According to the linear and logistic regression analysis results, the CRB-65 score was significantly correlated with HD (P<0.001), admission to ICU (P=0.014), LOS in ICU (P<0.001) and MV (P=0.004). The AUROC curve of CRB-65 was not higher than the other previous prognostic predictors (AUROC, 0.69), but the result was not different from the predictors. Conclusion The CRB-65 score is one of the prognostic indicators of acute HF in the ED. However, its prognostic predictive power remains limited.