Transitional cell carcinoma (TCC) is an extremely rare gynecologic tumor, particularly in the endometrium. All endometrial TCC cases reported so far in the literature were diagnosed at relatively advanced stages. In the present article, we report a pure primary endometrial TCC initially revealed by an abdominal mass and classified as an International Federation of Gynecology and Obstetrics stage IA. The patient was successfully treated with surgery and adjuvant radiotherapy. This case highlights the importance of early diagnosis of gynecologic malignancies, offering satisfactory outcomes even in the rarest types for which evidence-based recommendations are lacking.