We herein report a rare case of papillary adenocarcinoma which occurred in the third portion of the duodenum. The patient was a 62-year-old Japanese male who was admitted due to vomiting and right lower abdominal pain. No abnormal findings were found in the laboratory examinations. After a diagnosis of primary duodenal carcinoma was made by radiologic, endoscopic and ultrasonographic studies, a pancreatoduodenectomy was performed. The histology of the resected specimen revealed papillary adenocarcinoma, with invasion reaching to the pancreatic body. Some characteristic features of the disease are also reviewed.