A 68-year-old woman with fecal occult blood was referred to Dokkyo Medical School Hospital. Colonoscopy demonstrated a flat lesion in the rectum, and endoscopic mucosal resection of the lesion was performed. Histologic examination revealed that it contained ectopic gastric mucosa, which had a gastric foveolar and glandular mucinous phenotype, as demonstrated by immunohistochemistry. Moreover, the lesion also contained CA19-9- and CK7-positive pancreatic duct-like components in the submucosal layer. The present case is the first report to describe ectopic gastric mucosa and pancreatic ducts concurrently arising in the rectum.