Pancreatic carcinoma is rarely associated with familial adenomatous polyposis (FAP). Ten patients with this association have been reported in the literature. However, detailed data were available in only a few cases. The first case of pancreatic acinar cell carcinoma associated with FAP is reported. A 51-year-old man who had undergone total colectomy and ileoproctostomy for colonic polyposis 29 years previously was admitted with a cancer in the residual rectum. Preoperative examinations revealed a tumor in the head of the pancreas. Pancreaticoduodenectomy and very low anterior resection of the rectum were performed. Histologically, the tumor of the pancreas was acinar cell carcinoma. In patients with FAP, we recommend careful surveillance of not only the gastrointestinal tract but also of other organs such as those of the pancreaticobiliary system and the endocrine organs.