A 67-year-old man visiting our hospital with the chief complaint of sudden upper abdominal pain was diagnosed with acute pancreatitis. Based on computed tomography findings, intraductal papillary mucinous neoplasm(IPMN)was suspected as the cause of the pancreatitis and detailed examination was conducted following its alleviation. Endoscopic retrograde and magnetic resonance cholangiopancreatography showed marked dilation of the main pancreatic duct, with a mural nodule inside the main pancreatic duct at the pancreatic head. Main duct IPMN was diagnosed and pancreaticoduodenectomy was performed 3 months after the onset of acute pancreatitis. The histopathological findings showed a tumor proliferating in a mold pattern in the lumen of the dilated main pancreatic duct, resulting in a diagnosis of intraductal papillary mucinous carcinoma(IPMC). The presence of IPMN should be considered as a cause of acute pancreatitis; if findings suggestive of IPMN are found on imaging, detailed examinations and treatment are needed in consideration of the potential for malignancy following alleviation of pancreatitis.