Intraductal papillary mucinous neoplasm of the pancreas (IPMN) is a precancerous lesion with a well-described adenocarcinoma sequence. The rate of progression of IPMN appears to be very slow; however, patients with IPMN may be at increased risk for extrapancreatic malignancies. A 55-year-old female was diagnosed with IPMN of the pancreas and a duodenal polyp in 2004. After an approximate 3 year loss to follow-up, she was readmitted for managing abdominal pain and underwent Whipple's operation. Herein, we report a case of a patient with malignant IPMN accompanied by duodenal adenocarcinoma arising from a duodenal polyp. (Korean J Gastrointest Endosc 2011;42:268-273)