We report a unique carcinosarcoma of the ovary having an organoid growth pattern that resembled immature teratoma. The tumor contained both adenocarcinoma and squamous carcinoma (focally sebaceous) admixed with chondrosarcoma, rhabdomyosarcoma, and malignant neuroectodermal components. The neuroectodermal components were prominent, resembling ependymoblastoma, medulloepithelioma, ganglioneuroblastoma, glioblastoma multiforme, and pigmented neuroectodermal tumor. Immunohistochemical studies dramatically revealed carcinoma and rhabdomyosarcoma admixed with malignant neuroectodermal tumor. Implants of papillary serous carcinoma (with psammoma bodies) were present in the opposite ovary, uterine serosa, omentum, and appendiceal serosa. Although a variant not previously described in the ovary, this ovarian carcinosarcoma closely resembled nasopharyngeal tumors described as teratoid carcinosarcoma or terato-carcinosarcoma.