46 XY gonadal dysgenesis patients often develop gonadal tumors, including gonadoblastoma and other types of germ cell tumors. We report a case of a 16-year-old female adolescent with primary amenorrhea and a right adnexal mass. Subsequent study revealed that she is a 46 XY phenotypic female adolescent with complete gonadal dysgenesis and with no alterations of the sex-determining region Y gene. Microscopic examination of the gonads revealed bilateral gonadoblastoma mixed with dysgerminoma and mature teratoma. The tumor in the right gonad was also mixed with yolk sac tumor and immature teratoma with rhabdomyoblastic components, mimicking adult rhabdomyoma and rhabdomyosarcoma. No metastasis in the regional lymph nodes was identified and the patient is disease free 15 months postsurgery. The complexity of the tumorigenesis in this case indicates that the gonadal cells in gonadal dysgenesis are extremely unstable and highly tumorigenic. This tumorigenesis is not necessarily associated with sex-determining region Y gene alterations; therefore, it reinforces the recommendation of gonadectomy for gonadal dysgenesis patients, regardless of the sex-determining region Y gene status.