Although simultaneous endometrial and ovarian tumors are observed occasionally, rarely are the two neoplasms histologically disparate. We report a case of simultaneous endometrial malignant mixed mesodermal tumor and ovarian serous adenocarcinoma with a single right external iliac lymph node metastasis. Using immunohistochemical profiles, we demonstrated that the two tumors are separate primary neoplasms and identified the origin of the metastatic deposit as the mixed malignant mesodermal tumor.