Solitary fibrous tumor is a rare mesenchymal malignancy that may be found in many locations other than the pleura. The majority of these tumors have benign features, but some have malignant potential. We report a histologically proven case of a solitary fibrous tumor in a 52-year-old woman that was incidentally detected by chest radiography during a routine health check. Left posterolateral thoracotomy was performed and then the mass was completely removed. His postoperative recovery was uneventful.