A 43-year-old-man was diagnosed as having primary mediastinal nonseminomatous germ cell tumor based on percutaneous biopsy and an elevated serum concentration of alpha-fetoprotein (AFP). Although AFP decreased after chemotherapy, the mass size grew and developed tracheal compression by the tumor. The patient was treated with mechanical ventilation and subsequent stent implantation for keeping airway patency. After three cycles of chemotherapy and normalization of AFP, the increased mass was successfully resected and the pathological examination demonstrated a mature teratoma. This case showed a rare clinical manifestation of mediastinal growing teratoma syndrome and successful outcome by multimodal therapies.