Introduction: Although different scores have been suggested to predict outcomes in the setting of upper gastrointestinal bleeding (UGIB), few comparative studies between simplified versions of older scores and recent scores have been published. We aimed to evaluate the accuracy of pre- (PreRS) and postendoscopic Rockall scores (PostRS), the Glasgow-Blatchford score (GBS) and its simplified version (sGBS), as well as the AIMS65 score in predicting different clinical outcomes. Methods: In this retrospective study, PreRS, PostRS, GBS, sGBS, and AIMS65 score were calculated, and then, areas under the receiver operating characteristic curve were used to evaluate the performance of each score to predict blood transfusion, endoscopic therapy, surgery, admission to intensive/intermediate care unit, length of hospital stay, as well as 30-day rebleeding or mortality. Results: PreRS, PostRS, GBS, and sGBS were calculated for all the 433 included patients, but AIMS65 calculation was only possible for 315 patients. Only the PreRS and PostRS were able to fairly predict 30-day mortality. The GBS and sGBS were good in predicting blood transfusion and reasonable in predicting surgery. None of the studied scores were good in predicting the need for endoscopic therapy, admission to intensive/intermediate care unit, length of hospital stay, and 30-day rebleeding. Conclusions: Owing to the identified limitations, none of the 5 studied scores could be singly used to predict all the clinically relevant outcomes in the setting of UGIB. The sGBS was as precise as the GBS in predicting blood transfusion and surgery. The PreRS and PostRS were the only scores that could predict 30-day mortality. An algorithm using the PreRS and the sGBS as an initial approach to patients with UGIB is presented and suggested.