Metastatic carcinoma from the female genitalia to the oral mucosa is exceptionally rare, with only 11 such cases having been previously reported in the English-language literature. We describe a new case in a 65-year-old woman with a history of endometrial carcinoma who presented with swelling of the retromolar pad. Radiographic examination showed slight opacities and irregular trabecular bone in the left posterior mandible. Following an incisional biopsy, histologic examination and immunohistochemical studies revealed glandular adenocarcinoma with positivity for progesterone receptor, estrogen receptor, and cytokeratin 7. The patient was referred to her primary care physician for comprehensive treatment. This case illustrates the value of considering cancer metastasis in the differential diagnosis of an oral swelling, particularly in a patient with a history of cancer.