Abstract: Objective To study the clinicopathological features of ovary and uterus malignant mullerian mixed tumor (MMMT), and investigate its diagnosis and prognosis. Methods Twelve cases with ovary and uterus malignant mullerian mixed tumor in department of pathology, Chinese PLA General Hospital from 2008 to 2013 were enrolled in this study, their macroscopy, microscopy and immunohistochemistry were investigated, and clinical data and literatures were reviewed. Results The average age of MMMT cases was 59.6 years (range from 43 to 74 years). Of the 12 cases, 3 cases were uterus MMMT, 8 cases were unilateral ovary and 1 case was both ovaries and cervix MMMT. The patients usually presented with abnormal vaginal bleeding, abdominal pain and pelvic mass with no specifcity in clinic. The morphological changes included epithelial and mesenchymal components. Of the 12 cases, 6 cases were serous papillary carcinoma, 1 case was squamous cell carcinoma, 5 cases were endometrioid carcinoma and 2 cases had chondrosarcoma, 4 cases had leiomyosarcoma, 2 cases had rhabdomyosarcoma, 3 cases had endometrial stromal sarcoma, and 1 case had endometrial stromal sarcoma mixed chondrosarcoma. Immunohistochemically, CK was positive in all epithelial components, Vimentin was positive in all mesenchymal components, H-caldesmon was positive in leiomyosarcoma, Desmin was positive in rhabdomyosarcoma, CD10 was positive in endometrial stromal sarcoma, and S-100 was positive in chondrosarcoma. The main treatment was surgery plus chemotherapy. Ten cases were followed up (2 cases lost follow-up), 1 case died within one month after surgery, 7 cases relapsed during six to ffty-eight months and 2 cases had no tumor progression and metastasis during one and two years after surgery. Conclusion MMMT is a rare subtype of malignant epithelial mesenchymal mixed tumors. Because its clinical features are unspecifc, fnal diagnosis need pathological and immunohistochemical staining and its prognosis is extremely poor.