The patient was a 70-year-old woman who was found to have 2 mediastinal tumors on chest computed tomography(CT). One was located in the anterior mediastinum, and the other was in the upper mediastinum. Based on previous imaging studies, it was revealed that the 2 tumors had been increasing in size for 5 years. Thymectomy via median sternotomy was performed. Histopathologically, 3 tumors revealed to be in the thymus without direct invasion of the adjacent organs. All were thymic squamous cell carcinomas of 3.0×1.8×1.6 cm, 2.5×1.6×1.2 cm and 0.7 cm in size. No lymphatic invasion was observed and all tumors were pathologically stage I. Thus, we considered the 3 tumors were multi-centric primary tumors.