Bouveret's syndrome is a gastric outlet obstruction caused by an impacted gallstone that passes through a cholecysto-gastric or cholecysto-duodenal fistula. An elderly woman visited a local clinic with nausea and abdominal pain. Abdominal computed tomography revealed a stone that was impacted in the duodenal lumen and a fistula between the gallbladder and duodenum. Malignancy could not be excluded due to the mass in the cystic duct showing enhancement and the presence of enlarged lymph nodes on computed tomography, and increased fludeoxyglucose uptake in the cystic duct on positron emission tomography. The patient underwent simultaneous cholecystectomy, segmental duodenectomy and gastro-jejunostomy. Pathological examination exhibited chronic inflammation and no primary cancer of the gallbladder and fistula.