We report the case of a 65-year-old woman who had a high level of serum pepsinogen II. Several months earlier, she had found a mass on the right side of her upper abdomen. Esophagogastroduodenoscopy did not reveal atrophic or inflammatory findings. She had not taken proton pump inhibitors, and there was no indication of renal dysfunction. Imaging tests showed a mass of approximately 80mm in the pancreatic head. We performed pancreatoduodenectomy, and the histopathological examination revealed an intraductal papillary mucinous neoplasm (IPMN) of gastric type. Serum pepsinogen II levels substantially lowered after surgery. To the best of our knowledge, this is the first report on a relationship between IPMN and serum pepsinogen II.