Uterine carcinosarcoma (malignant mixed mullerian tumor) is uncommon. We report the case of a 17-year-old patient who complained of pelvic pain and abnormal genital bleeding, and had a voluminous hemorrhagic tumor protruding through the vaginal os. Hysterectomy was performed. The histopathologic and immunohistochemical evaluation led to the diagnosis of uterine carcinosarcoma. Adjuvant chemotherapy was given. In spite of the surgical treatment, the evolution was fatal with widespread metastases. From data of the literature, we discuss the diagnosis, histogenesis and treatment of this rare tumor.