Gallbladder adenocarcinomas in two captive African lions (Panthera leo), an 18-yr-old male and a 17-yr-old female, are described in this report. Grossly, both lions had hemoperitoneum with thickened and sclerotic gallbladder walls. Histopathologically, the male's tumor was well differentiated and the female's was poorly differentiated with multinucleate giant cells. Both tumors were highly invasive and involved the gallbladder serosa. The male also had a tumor in the liver, and the female's tumor had disseminated to the serosal surfaces of abdominal organs. In both cases, neoplastic cell cytoplasm stained diffusely for cytokeratin AE-1/AE-3 and cytokeratin 7 and granularly for lysozyme on immunohistochemical staining.