We report the case of a rectal teratoma. A 62-year-old woman was referred to our department for evaluation of a rectal mass. She had a 3-month history of rectal bleeding and constipation. No palpable mass was detected using digital rectal examination. Colonoscopic examination demonstrated a protruding mass with a broad stalk in the posterior wall about 12 cm from the anal verge. A computed tomography scan showed a mass, which contained calcifications and fatty components, protruding into the rectal lumen. On operation, the mass was located in the upper rectum, and the right lateral portion of the upper rectum was adhesed to the right ovary. Thus, she had undergone a low anterior resection and right oophorectomy. The pathologic results confirmed a teratoma arising in the muscularis mucosa and the submucosa of the rectal wall.