Ovarian stroma and surface epithelium develop from two different embryological primordia and give rise to tumors of distinct characteristics. The simultaneous presence of two kinds of ovarian tumors in one patient is rare. Concurrent presence of a large ovarian fibroma in one ovary, and a serous cystadenoma in the seemingly normal-looking contralateral ovary was found in a 55-year-old woman. The unusual coexistence of these tumors warrants a closer and longer follow-up of the patient. To the best of our knowledge, this is the fourth case to be reported in the literature. All surgically isolated tissues should undergo detailed histopathological examination, including normal-looking tissues which are excised as a part of the procedure.