We report a case of dedifferentiated liposarcoma of the spermatic cord. A 79-year-old man was referred to our hospital with the chief complaint of a painless right scrotal swelling. A hard mass was palpable beside the soft mass which was suspected of lipoma or liposarcoma, and under this mass there was right testis. Therefore, we performed a right radical orciectomy. Histopathological diagnosis was dedifferentiated liposarcoma of the spermatic cord. Dedifferentiated liposarcoma of the spermatic cord was rare, and preoperative diagnosis was difficult.