Pseudo-Meigs' syndrome is a syndrome rarely caused by leiomyomas. Elevated CA125 usually suggests malignancy of the ovary. No reported case of pseudo-Meigs' syndrome presenting with necrosis and mucinous degeneration of uterine cellular leiomyomas (CLs) and an elevated CA125 level was found upon a PubMed search. A 37-year-old woman presenting with massive ascites, bilateral pleural effusions and a pelvic mass measuring 20 x 18 x 10 cm is described. The pre-operative serum CA125 was 920.4 U/ml. After total abdominal hysterectomy and partial omentumectomy, the final pathologic diagnosis was CL with focal hemorrhage, necrosis and mucinous degeneration. The ascites and pleural effusion disappeared, and the CA125 level returned to normal in one month. Benign leiomyoma accompanied by pseudo-Meigs' syndrome and elevated serum CA125 can mimic a pelvic malignancy.