Abstract: Mixed germ cell tumor (MGCT) is a rare type of malignancy that occurs in many parts of the body with a high degree of malignancy but no specific clinical manifestations and typical imaging features. At present, no cases of MGCT originating in the thoracic cavity have been reported in the literature at home and abroad. The authors reported a case of giant MGCT of the left thoracic beside the mediastinum, whose pathologial components were yolk sac tumor and teratoma. This paper analyzed the characteristics of MGCT from imaging features, clinical manifestations and pathological features, combined with relevant literature reports to improve the abilities of MGCT diagnosis and treatment.