Objective Primary malignant mediastinal germ cell tumors (MMGCTs) are rare in children and adolescents and have a poorer prognosis than their gonadal counterparts. We report a single institutional experience of a 10-year period of primary advanced MMGCTs treated with chemotherapy, followed by radiotherapy in those who had residual mass. Methods Children and adolescents with primary advanced MMGCTs between 2005 and 2014 were identified from the Cancer Center, Sun Yat-Sen University. Medical records were reviewed for clinicopathological characteristics, treatments, and outcomes. Results Twenty-four children and adolescents with either stage III or IV primary advanced MMGCTs met the inclusion criteria. There were 23 males and one female with a median age of 16 (range 10-18). Seven cases were seminomas (29.2%); four (16.7%) yolk sac tumors (YST); three (12.5%) choriocarcinomas; and ten (41.6%) nonteratomatous combined germ cell tumors (CGCTs). All patients were treated with first-line cisplatin-based chemotherapy regimens (PEB: 19, VIP: 5). Thirteen (54.2%) and Twelve (50%) patients received surgery and radiotherapy, respectively. With a median follow-up of 46.2 months (range 9.6-124.8 months), a total of five (20%) patients died of disease progression; the five-year overall survival (OS) and disease-free survival (DFS) rates were 82.3% and 64.9%, respectively. - Seven patients with seminoma GCTs received post-chemotherapy irradiation were alive with sustained CR (5-year OS and DFS, 100%, respectively). Five patients with NSGCTs were administered irradiation and one relapsed 35 months later and died of metastasis (5-year OS, 100%; 5-year DFS 66.7%). Univariate analysis identified histology and stage were prognostic factors. Conclusion Multimodality treatment approach of chemotherapy followed by radiation consolidation ensured long-term survival in primary advanced MMGCTs. Further research is warranted to improve the prognosis of children with primary advanced MMGCTs.