The patient was a 68-year-old man with pancreatic cancer exhibiting invasion into the superior mesenteric artery and stenosis of the third part of the duodenum. He subsequently received a duodenal stent for malignant gastric outlet obstruction. On day 43 after the placement of the duodenal stent, he reported feeling poorly, with hypotension and hematemesis. High-density areas were observed from the stomach to the rectum on computed tomography. We diagnosed the origin of bleeding as the last third of the duodenum; unfortunately, the patient died. This is the first report of massive gastrointestinal tract bleeding as a late complication of self-expandable metallic stent placement for malignant gastric outlet obstruction.