A 38-year-old female patient experienced groin pain; ultrasound imaging revealed a dermoid cystic mass in the right ovary and a cystectomy was then performed. Unusually, a mature cerebellum is found in the cyst wall. The pathological diagnosis was 'mature cystic teratoma with well-differentiated cerebral and cerebellar tissue'. Glial tissue is a common neural component of teratomas, but a cerebellum is extremely rare in mature ovarian cystic teratomas. The authors report the case because of its rare component; they acknowledge that a cystic teratoma is the most common neoplasm of ovarian germ cells.