A case of heterotopic gastric mucosa in the fundus of the gallbladder is reported. A 23-year-old man, who had been healthy and asymptomatic, visited our hospital because of abnormal findings in a liver enzyme test given during a routine health screening. Ultrasonography demonstrated a highly echogenic polypoid mass in the fundus of the gallbladder. The gallbladder mass was confirmed by both computed tomography and intravenous cholangiogram. After a 10-month follow up, laparoscopic cholecystectomy was performed. Intraoperative touch smear cytology of this lesion revealed class II cells. The surgical specimen revealed a 15 x 10 x 5 mm polypoid lesion in the fundus, with no gallstones in the gallbladder. Histologically, the polypoid lesion consisted of both fundic type and pyloric type gastric glands located in the mucosa of the gallbladder. In the literature, 42 cases of heterotopic gastric mucosa of the gallbladder have been reported, only 3 of which, including this present case, were found incidentally, with no apparent symptoms.