The origin of a malignant fibrous histiocytoma in the anterior mediastinum is rare. A 71-year-old man was referred to our department for treatment of a tumor 15 cm in diameter originating in the anterior mediastinum. Malignant fibrous histiocytoma was suspected after a percutaneous needle biopsy. Systemic screening showed no other organ involvement, and the tumor was considered to be a primary mediastinal tumor. The tumor, resected through a median sternotomy, was well encapsulated and resection was complete. The pathological diagnosis was malignant fibrous histiocytoma originating in the anterior mediastinum.