A 55-year-old woman underwent a total hysterectomy, bilateral salpingo-oophorectomy, partial omentectomy, and lymphadenectomy for endometrial cancer. Histologically, the cancer was endometrioid adenocarcinoma grade 1, which invaded the myometrium. There was no macroscopically detectable mass in the ovaries. However, histological examination revealed a small tumor, 1 mm in size, in the medulla of the right ovary. The ovarian tumor was composed of uniform epithelioid cells that grew in nests. Vessels of various sizes were observed within the tumor, and they were surrounded by tumor cells. Immunohistochemically, the ovarian tumor was positive for smooth muscle actin and vimentin but negative for desmin and CD34. Based on these findings, the authors made the diagnosis of ovarian glomus tumor. Although an ovarian glomus tumor is extremely rare, the authors believe that it should be included in the differential diagnosis of ovarian mesenchymal tumors and sex cord tumors.