The Mediastinal lipoma is an uncommon tumor in the literature. The literaure concerning mediastinal lipomas began with the first case report by Fothergill in 1781 and about 120 cases had been reported till 1969. We experienced one case of huge mediastinal lipoma, which was 885gm in weight, The mass was successfully removed through the right posterolateral thoracotomy and pathologic report confirmed pure adipose tissure. The patient`s postoperative course was uneventful and he was discharged on the 17th day.