Several scoring systems are used to predict critical care requirements in coronavirus disease 2019 (COVID-19) patients. This study aims to determine the relationship between the hemoglobin, albumin, lymphocyte, and platelet (HALP) scores and in-hospital mortality for COVID-19 patients who visited the emergency department (ED). This retrospective study included patients over 18 years of age. Data were scanned into a digital information system of the hospital. The area under the receiver operating characteristic (ROC) curve and the area under the curve (AUC) were used to measure each discriminant cutoff value to predict mortality. A total of 458 patients were included in this study. The mean age of the patients was 72 years, and 216 (47.2%) patients were women. ROC analysis was performed to examine the predictive power of the HALP score in predicting mortality in COVID-19 patients, with an AUC of 0.720 (95%confidence interval: 0.676–0.761), a Youden index of 0.357, and a p value of 0.001. As a result of the statistical analysis, it was determined that the HALP score was statistically significant in the prediction of mortality in COVID-19 patients (p < 0.001). In this study, we found that the HALP score could be a good predictor of in-hospital mortality among COVID-19 patients.