Pancreaticoduodenal artery aneurysm (PDAA) is a rare disease that is recognized as an intra-abdominal hemorrhage differential diagnosis. This case study reports on a ruptured PDAA case in which ultrasonography (US) proved useful for the initial diagnosis. A 60-year-old man presented to the emergency department with pain in the epigastrium and back. An abdominal US performed at presentation suggested a PDAA and intraperitoneal hemorrhage/retroperitoneal hematoma. In addition, a contrast-enhanced computed tomogram (CT) revealed a hematoma extending from the upper abdomen to the pelvic floor and an aneurysmal pancreaticoduodenal artery arcade dilatation. Furthermore, emergency abdominal angiography findings revealed bleeding from a posterior-inferior PDAA, and coil embolization was performed. Postoperative progress was good, and the postoperative CT at 7 days showed no rebleeding signs and/or enlargement or new PDAA development. Therefore, the patient was discharged from the hospital 14 days after embolization.