Synchronous bilateral testis tumors of different histologic types are rare. All previous cases have demonstrated germ cell tumors on both sides. The simultaneous appearance of a germ cell tumor and a contralateral non-germ cell tumor has not been reported. We herein report a thirty-four-year-old man who presented with a mixed non-seminomatous germ cell tumor of the left testis and theca cell tumor of the right testis.