Malignant germ cell tumors of the ovary are rare gynecologic tumors usually affecting younger women. Recently, we experienced a case of 11-year old female with mixed germ cell tumor of ovary which was composed of yolk sac tumor and immature teratoma with high serum levels of α-fetoprotein (AFP) and human chorionic gonadoprotein (hCG). We report this case with brief review of concerned literature.