Fibrothecomas are mostly benign ovarian tumors. We describe a rare case of fibrothecoma in a 59-year-old woman with a history of recurrent massive ascites and postmenopausal bleeding. Over 2 years she has undergone more than 50 paracenteses with 8-11 L withdrawn each time. She presented with a newly diagnosed pelvic mass and bilateral hydrosalpinges demonstrated on ultrasound and were confirmed with computed tomography. The pelvic magnetic resonance imaging showed a large complex cystic mass arising from the left ovary measuring 16.6 × 12.1 × 8.6 cm3 with an area of irregular mural enhancement. The patient underwent left salpingo-oophorectomy with benign frozen section results. The final pathology was consistent with cystic degeneration of fibrothecoma.