Primary leiomyoma of the ovary, which is of unknown origin, is an extremely rare tumor of ovary. We report a rare case of giant primary ovarian leiomyoma with an unusual presentation, ascites, elevated CA125 and discuss the preoperative imaging findings. A 45-year-old woman was referred for evaluation of an adnexal mass of 8 x 9 cm with ascites and elevated CA125 levels. Preoperative imaging studies were in accordance with fibroma/thecoma. At laparotomy total abdominal hysterectomy and bilateral salpingo-oophorectomy were performed. Histological and immunhistochemical examination revealed primary ovarian leiomyoma.