Primary angiosarcoma of the female reproductive system is extremely rare, and its management is not well understood. We experienced a very rare case of angiosarcoma arising in the uterus of a 37-year-old woman who presented abdominal distension. At laparotomy, the uterus was observed to be enlarged and deformed by multilobulated hemorrhagic mass. Tumor deposits were present on both ovaries and the omentum. The operation consisted of total abdominal hysterectomy with salpingo-oophorectomy, and omentectomy. Microscopic examination showed that the tumor consisted mostly of solid sheets of pleomorphic and spindle cells forming irregular, communicating cleft-like spaces. Well-formed vascular channels lined by atypical endothelial cells were seen in differentiated areas. Some vessels were partially lined by normal endothelial cells and partially by neoplastic endothelial cells. Papillary architecture composed of epithelioid tumor cells was noted in a focal area. The tumor cells were immunoreactive for factor VIII-related antigen, Ulex europaeus agglutinin-1, CD31 and CD34. Weibel-Palade bodies were not seen in the tumor cells. She received adjuvant chemotherapy, but died 13 months after the diagnosis.