We report the case of a sarcomatoid carcinoma with a rhabdoid tumor component originating in the gallbladder, along with immunohistochemical and electron microscopic findings. A 61-year-old woman presented with a 5-month history of right upper quadrant pain. Ultrasonography and a computed tomographic scan indicated gallbladder cancer. She underwent a cholecystectomy and a common bile duct resection. A firm mass (4.5 cm in greatest dimension) was present in the neck portion of the gallbladder. The mass was firm, solid, yellowish gray, and granular with areas of necrosis. Microscopically, the tumor was a biphasic sarcomatoid carcinoma and consisted of diffusely arranged pleomorphic cells, focally showing rhabdoid features and neoplastic glands with focal mucin production. Heterologous components such as osteoid, chondroid, and rhabdomyoblastic elements were not identified. By immunohistochemical staining, we demonstrated that the rhabdoid cells coexpressed cytokeratin and vimentin. On electron microscopic examination, the rhabdoid tumor cells showed cytoplasmic whorls of intermediate filaments in the cytoplasm and eccentric nuclei. Two months postoperatively, the follow-up computed tomographic scan showed multiple intrahepatic metastases and omental seedings.