We report a case of a mixed tumor of paratesticular rhabdomyosarcoma and an adenomatoid tumor in an elderly patient. Rhabdomyosarcoma is one of the most common childhood tumors; however, it rarely occurs in the elderly. In addition, to our knowledge, paratesticular rhabdomyosarcoma and adenomatoid tumor rarely form mixed tumors. Finally, we consider the pathogenesis of diploblastic tumors.