We describe a distinctive polypoid lesion of the gallbladder (16 mm in diameter) at the fundus, associated with a granulomatous mass in the liver adjacent to the gallbladder fossa, in a 64-year-old Japanese woman. Preoperatively, the lesion was diagnosed as advanced gallbladder cancer infiltrating the liver, and hepatopancreato-duodenectomy was performed. In the resected specimen, the polyp was round and pedunculate in shape, and, microscopically, it consisted of a mixture of small glandular and surrounding muscular elements, but atypia was not noted. The constituent elements were identical with those of adenomyoma, but the polypoid appearance was unusual. The hepatic lesion proved to be a foreign body granuloma containing multiple barium fragments and giant cells. A deep gastric ulcer, which penetrated into the gallbladder fossa, was also noted, near the granuloma. The histologic features indicate that the polypoid appearance of the tumor was due to a secondary modification of pre-existing adenomyoma by hepatic granuloma. To our knowledge, this is the second reported case of an adenomyomatous lesion of the gallbladder with a polypoid appearance.