Mediastinal solitary fibrous tumors (SFTs) are rarely found in adults and there are few reports describing primary mediastinal SFT invading the diaphragm. We report the case of a 47-year-old woman with a large right inferior mediastinal SFT. Magnetic resonance imaging showed the tumor invading the right lower lobe of the lung and the right hemidiaphragm, with displacement of the inferior vena cava (IVC) and right lobe of the liver. Angiogram showed IVC stenosis. To our knowledge, this is the first report of complete resection of the tumor combined with right lower lobectomy of the lung and partial resection and reconstruction of the right diaphragm with a Dacron flap.