The Brenner tumor is an uncommon ovarian tumor in pregnancy with only three previous cases in the English published reports. A 35-year-old woman delivered abdominally because of distress symptoms and a Brenner tumor was resected incidentally. Histological examination revealed a tumor composed of epithelial nests and areas of stromal luteinization. The patient was treated conservatively. Brenner tumor should be considered in the differential diagnosis of adnexal masses during pregnancy. These tumors are mainly benign and show typical luteinization associated with the hormonal milieu in pregnancy.