Primary mediastinal non-seminomatous germ cell tumors (PMNSGCT) are rare but life-threatening thoracic cancers. We report our experience from eight patients with peri-treatment adverse events. By analyzing changes in tumor extent, serum tumor markers, and pathologies between diagnosis and transfer, those events could be attributed to postbiopsy respiratory insufficiency, growing teratoma syndrome, secondary histiocytic malignancy, and PMNSGCT progression. Subjecting patients to respiratory therapy, conventional or high-dose chemotherapy, and surgery controlled the disease, with five of the eight patients surviving disease free. These outcomes indicate that integrated appropriate and timely approaches are important in tackling peri-treatment adverse events.