Fourty-seven years old male was admitted to this hospital with the symptoms of worsening cough and chest pain. An anterior mediastinal tumor, 13 cm in diameter, was pointed out on chest X-ray. The tumor was diagnosed as primary mediastinal germ cell tumor with mixed seminomatous and non-seminomatous elements due to elevated serum AFP and beta HCG, and the pathological finding of needle biopsy specimen. He underwent 3 courses of chemotherapy with BEP regimen, and following surgical resection of the tumor, left upper lobectomy and partial resection of pericardium via median sternotomy. Pathological diagnosis of the resected tumor was mature cystic teratoma. For 9 months no recurrence of the tumor has been observed.