Large cell neuroendocrine carcinoma of the ovary is a rare recently established entity. Few cases have been reported in the literature, and they are usually associated with another type of surface epithelial tumor. The association of a large cell neuroendocrine carcinoma with a surface epithelial tumor and a teratoma is even rarer, with only two cases previously described. We report the cases of two patients in their fifties who presented with a growing abdominal mass and died of metastatic disease within less than a year. Histological assessment revealed large cell neuroendocrine carcinoma admixed with mucinous adenocarcinoma and teratoma. Different hypotheses regarding the origin of large cell neuroendocrine carcinoma of the ovary are discussed. The immunohistochemical pattern of staining for cytokeratin 7 and cytokeratin 20 suggests that the composite epithelial tumors originated from the pre-existing teratoma.