Some children with profound and long-standing hypothyroidism present with signs of paradoxical sexual maturation. In females, it is characterized by breast development, vaginal bleeding, lack of pubic hair, and delayed bone age. A case of multiple ovarian cysts in a prepubertal girl with severe hypothyroidism due to autoimmune thyroiditis is reported. A 7-year, 8-month-old girl presented with precocious puberty and vaginal bleeding. A pelvic ultrasound revealed markedly enlarged ovaries with numerous cysts which disappeared dramatically after thyroid replacement. When large multiple ovarian cysts with vaginal bleeding are found in a prepubertal girl who has a retarded bone age, the possibility of associated hypothyroidism should be considered. Health care providers should keep this in mind because this constellation of symptoms can be completely reversed with the initiation of thyroid replacement.