This report presents an unusual case of life-threatening massive bleeding in the pulmonary trunk adjacent to the right ventricular outflow tract during resection of a large primary mediastinal nonseminomatous germ cell tumor (PMNSGCT) in the absence of cardiovascular surgeons. The patient was a 21-year-old male whose large mediastinal tumor was diagnosed as an extragonadal PMNSGCT, which was a mixture of a yolk sac tumor and an immature teratoma. Generally, chemotherapy causes extensive peripheral tumor necrosis of PMNSGCTs, thus enabling their complete resection.