Tuberculosis is one of the most common chronic disease. While the disease process may involve anywhere of the body, tuberculosis of anterior mediastinum which forming tumor like mass was not recognized commonly. We experienced a surgical case of tuberculous empyema thoracis at anterior mediastinum in 16 year old boy. Preoperatively, he was diagnosed to anterior mediastinal tumor such as teratoma or dermoid cyst by routine study. Operation was performed by midline sternotomy extending over right 4th intercostal space. The mass was elongated football shaped [20x16x15] and markedly adhered to right side of pericardium, upper 8< lower lobe of the right lung. Opening the mass, enormous pus-like material was evacuated and excised segmentally with decortication. Postoperative pathologic diagnosis was tuberculous empyema thoracis and granuloma.