An 83-year-old man was referred to our hospital for a detailed evaluation for vomiting. Esophagogastroduodenoscopy and abdominal computed tomography showed duodenal stenosis with wall thickness. Biopsy including endoscopic ultrasound-guided fine-needle aspiration of the thickened wall showed inflammation without malignancy. During the clinical course, wall thickening of the distal bile duct appeared. Biopsy under endoscopic retrograde cholangiography showed papillary adenocarcinoma. Surgery revealed that the tumor had widely invaded the duodenal wall from the outside; therefore, only gastrojejunostomy was performed. It was hypothesized that the cholangiocarcinoma had progressed to the serosal side, disseminated in the peritoneum, infiltrated the duodenal serosa, and caused duodenal stenosis.