Primary ovarian angiosarcoma is very rare with only 27 cases reported so far in the medical literature. We report here on a rare case of ovarian microinvasive mucinous carcinoma that was coexistent with angiosarcoma in a 54-year-old woman. The tumor was a 26x19x10 cm-sized multilocular cystic mass with a 4x3 cm-sized solid hematoma-like nodule in the center. Microscopically, it was composed mostly of mucinous tumor of various grades from borderline to microinvasive carcinoma. The hematoma-like area turned out to be an angiosarcoma, composed of pleomorphic cells that formed slit-like spaces, spindle cells that formed short fascicles and anastomosing vascular channels with atypical endothelial cells. All these cells were positive for CD31, CD34 and factor VIII-related antigen. The patient developed peritoneal and pleural metastases, which were angiosarcoma and mucinous carcinoma, respectively. We believe this case is only the fourth example of an ovarian collision tumor of angiosarcoma and surface epithelial tumor.