We report a rare case of pseudo-Meigs' syndrome due to metastasis of breast cancer to both ovaries. A 34-year-old woman with exertional dyspnea was admitted to our hospital. Before entry the patient had undergone radical mastectomy for left breast cancer in June 1998. Resection and reconstruction of the chest wall for recurrence of the breast cancer had been performed in April 2001. Right pleural effusion was found on admission to our hospital in October 2002. Continuous thoracic drainage obtained 500-2000 ml of fluid per day. Cytologic results were both normal and benign, and cultures for bacteria and acid-fast bacilli were negative. During treatment of the pleural effusion, which proved to be cryptogenic and intractable, a huge pelvic tumor was found. The primary site was unknown. Surgery was performed in November 2002, and tumors were removed from both ovaries. The right pleural effusion vanished after surgery. Pseudo-Meigs' syndrome with metastasis of breast cancer to both ovaries was diagnosed. The patient died of cachexia related to the carcinoma in January 2005.