We report an unusual case of a large, broad ligament uterine leiomyoma with cystic degenerations, masquerading as a malignant ovarian tumor on ultrasonography and CT with the diagnostic difficulties posed. A 40-year-old married female presented with complaints of abdominal distention and a palpable abdominopelvic mass occupying whole of lower abdomen. Ultrasonography and CT revealed a large solid mass with cystic areas extending into both uterine adnexa. The patient underwent a laparotomy. Gross examination revealed normal ovaries and a pedunculated mass with prominent cystic honeycomb degenerations, originating from the uterus. The tumor was excised through the peduncle and pathologic evaluation revealed a uterine leiomyoma with cystic degeneration. In conclusion, a large pedunculated leiomyoma with cystic degenerations can mimic a malignant ovarian neoplasm on imaging studies. Therefore, uterine leiomyoma with cystic degenerations should be considered during the differential diagnosis of large adnexal masses.