Gonadoblastoma is an uncommon benign gonadal neoplasm that has the potential for malignant transformation. While primary amenorrhea or virilizing symptoms are common in most female patients with gonadoblastoma, precocious pseudopuberty has been rarely reported as a presenting symptom in gonadoblastoma. We describe a case of ovarian gonadoblastoma in a 6-year-old girl who presented with precocious development of breast and vaginal bleeding. Serum estradiol rose markedly, whereas LH and FSH were within normal limit for her age. The karyotype analysis showed 46,XX. Ultrasonography and pelvic MRI revealed a well-marginated enhancing mass in the left ovary. Surgical resection of the left ovary was performed. Microscopic findings revealed the characteristic cellular nests consisted of large germ cells and small cells, which resemble immature Sertoli or granulosa cells. Additionally, Leydig cells were found in the stromal component of the tumor. These findings were consistent with gonadoblastoma. The patient had a favorable outcome following the operation.