Seminoma arising in an abdominally located undescended testis is uncommon, accounting for only 5% of all seminomas. It tends to be relatively advanced at the time of diagnosis and usually treated with surgery followed by radiation and/or chemotherapy. We report a case of 61-year-old man who had a giant seminoma arising in the right testis of bilateral intraabdominal undescended testes with retroperitoneal lymph node metastasis, which was successfully treated with initial BEP chemotherapy. Excision of residual masses revealed complete necrosis of the tumor without viable cancer cells. The patient has been free of recurrence for 5 years after surgery.