We report an extremely rare case of pseudo-Meigs' syndrome caused by a retroperitoneal tumor in a patient with Ebstein anomaly. A 60-year-old woman was admitted because of marked hydrothorax and ascites. She also had pleural effusion. Because echocardiography revealed Ebstein anomaly, medical treatment was performed, under the diagnosis of heart failure. However, her pleural effusion and ascites did not completely disappear. Computed tomography (CT) scan showed a round solid retroperitoneal pelvic mass, with a diameter of approximately 5 cm in the vesicouterine fossa. After resection of the tumor, which was histologically found to be fibroma, her pleural effusion and ascites disappeared.