Background: The aim of this study was to investigate the clinical characteristics and outcomes of patients with primary malignant mediastinal non-seminomatous germ cell tumor (MMNSGCT) by comparing the efficacies of different treatment modalities.Methods: The charts of 62 consecutive patients with MMNSGCT between 1990 and 2010 were reviewed.Analyses included Kaplan-Meier survival and Cox multivariate regression.Results: There was sufficient data of 61 patients for inclusion in the study.The median age was 25 years.At diagnosis, 35 patients had tumors located in the mediastinum, 26 had lung and/or distant metastases.At a median follow-up of 47.2 months, 32 patients had died and 43 had developed progressive disease.The one,three, and five-year overall survival (OS) and progression-free survival (PFS) rates were 72.1%, 50.8%, 49.2% and 47.5%, 32.8%, 32.8%, respectively.Patients who received radiotherapy in the primary treatment regimen showed improved five-year OS (68.2% vs.38.5%, P=0.043), PFS (45.5% vs.20.5%, P=0.023), and local recurrence-free survival (LRFS) (77.3% vs.38.5%, P =0.003) compared with those who did not receive radiotherapy.Multivariate analysis revealed that radiotherapy was an independent prognostic factor of five-year OS (hazard ratio [HR] 0.39,P =0.037), PFS (HR 0.42, P =0.017), and LRFS (HR 0.31, P =0.019).Conclusion: Radiotherapy in a chemotherapy-based treatment regimen could significantly reduce local recurrence and improve survival of MMNGCT patients.