Dysgerminoma developed in a 21-year-old phenotypic female patient with 46,XY pure gonadal dysgenesis, Swyer syndrome. This patient presented with pelvic mass associated with abdominal pain and primay amenorrhea. Clinical characteristics showed a typical stigmata of gonadal dysgenesis: primary amenorrhea, sexual infantilism, a small uterus and left streak gonad. A 46,XY karyotype was made by lymphocyte culture. The patient was counseled to undergo operation, chemotherapy and hormon therapy. She underwent bilateral gonadectomy with total hysterectomy, partial omentectomy and multiple pelvic wall random biopsy. Histological examination revealed dysgenetic gonads with dysgerminoma. After surgery, the patient received chemotherapy and also was started on hormone replacement therapy. She is currently alive with no evidence of disease after 19 months from surgery.