Background: Swyer syndrome, 46,XY gonadal dysgenesis, is a sex reversal disorder with a female phenotype. Germ cell tumors, including dysgerminoma, may arise in streak gonads of patients with gonadal dysgenesis. Case: A 22-year-old female patient with a 46,XY karyotype was admitted to hospital for primary amenorrhea and a pelvic mass. Laparotomy exploration revealed a hypoplastic uterus and a 80 × 70 × 60 mm mass in the right gonad with extension to the pelvic peritoneum. Histologic finding in frozen section was dysgerminoma. Debulking surgery with pelvic lymphadenectomy was subsequently performed and the patient was given four cycles of chemotherapy (bleomycin, etoposide, and cisplatin) post-operation. Conclusion: The presence of Y chromosome in patients with 46,XY gonadal dysgenesis may increase the risk of gonadal tumors. A prophylactic bilateral salpingo-gonadenectomy should be advised to those patients.