Pseudoaneurysms are uncommon but their rupture and bleeding can lead to serious complications and be fatal. We present here a case of a man in his late 70s who was transferred to our hospital with persistent gastrointestinal bleeding. One month prior to his admission, he had undergone surgery for a fracture to his left knee. Endoscopic examination found pulsating blood vessels on a duodenal ulcer, which suddenly ruptured and caused significant bleeding. Immediate endoscopic haemostasis was administered and the bleeding decreased. Considering the high rate of rebleeding that may occur with a pseudoaneurysm, the patient underwent interventional radiology that culminated in a diagnosis of a pseudoaneurysm originating from gastroduodenal artery (GDA); successful embolization was achieved. Tests showed that the patient had Helicobacter pylori infection. We hypothesised that the H. pylori infection had led to the occurrence of the duodenal bulb ulcer, and the patient’s left knee fracture and surgery a month previously had contributed to this predisposition for a pseudoaneurysm.