Objective: Gastrointestinal (GI) bleeding is one of the most common reasons for people to visit the emergency department. Despite advances in treatments, the intensive care unit (ICU) admission rates due to GI bleeding are still high. Therefore, many scoring systems had been developed to screen patients who need active care. Among these scoring systems, the AIMS65 score, Glasgow-Blatchford score (GBS), and Pre-Rockall score (PRS) are known to be accurate risk assessment scoring models. A recent study has shown that hypoalbuminemia is related to poor prognosis in patients with GI bleeding. In this study, we compared the prognostic performance of the blood urea nitrogen to serum albumin ratio (B/A ratio) with the AIMS65, GBS, and PRS scores in patients with GI bleeding. Methods: This is a retrospective cohort study of patients presenting with GI bleeding in the Seoul Regional Emergency room from February to December 2018. The baseline characteristics of these patients were obtained. The data were compared with the prevalence of ICU admission from the emergency department and in-hospital mortality. The B/A ratio, AIMS65, GBS, and PRS scores as predictors of ICU admission and in-hospital mortality were evaluated using the area under the receiver operating characteristic (AUROC) curve. Results: A total of 433 patients were included in this study. Of these, 354 (81.8%) were admitted to the hospital, 121 (27.9%) were admitted to the ICU, and 26 (6.0%) died during hospitalization. Multivariate logistic regression analysis revealed that the B/A ratio was a significant predictor of ICU admission and in-hospital mortality. The predicting ICU admission AUROC value of the B/A ratio was 0.735, and those of the AIMS65, GBS, and PRS scores were 0.763, 0.741, and 0.704, respectively. For predicting in-hospital mortality, the AUROC value of the B/A ratio was 0.758, and those of the AIMS65, GBS, and PRS scores were 0.826, 0.717, and 0.744, respectively. Conclusion The B/A ratio is a useful tool for predicting the prognosis for patients with GI bleeding as are the AIMS65, GBS, and PRS score models.