Duodenal ulcer bleeding has a higher risk of mortality than bleeding from other portions of the gastrointestinal tract. AIMS65 is an effective risk-scoring system to predict prognosis of upper gastrointestinal bleeding and can be easily calculated without endoscopic findings. In this study, we investigate the usefulness of AIMS65 to predict prognosis of patients with duodenal ulcer bleeding. Two hundred and fifty-five patients with endoscopically diagnosed duodenal ulcer bleeding at Kurashiki Central hospital from July 2007 to June 2017 were studied. We compared AIMS65, Glasgow Blatchford score (GBS), admission Rockall, and full Rockall scoring systems for predicting in-hospital mortality by calculating area under the receiver operating characteristic curve (AUROC). In-hospital mortality due to duodenal ulcer bleeding occurred in 17 (6.7%). Scores of all scoring systems were significantly higher in patients with in-hospital mortality than in patients without it. AUROC values for predicting in-hospital mortality was 0.83 in AIMS65, 0.74 in GBS, 0.76 in admission Rockall score, and 0.82 in full Rockall score, a statistically insignificant difference among the systems. In AIMS65, score more than or equal to 2 was an optimal value to predict in-hospital mortality, with sensitivities of 88.2% and specificities of 59.7%, respectively. AIMS65 predicted in-hospital mortality of patients with duodenal ulcer bleeding as accurately as did other scoring systems. Given its simplicity of calculation, AIMS65 may be a more clinically practical system in the management of bleeding duodenal ulcer patients.