Background: Primary Intracranial Germ Cell Tumors (iGCT) are rare. Previous prospective and retrospective studies mainly included pediatric patients (pts) with a median age of 10-14 years. The aim of this retrospective analysis was to evaluate characteristics, treatment and outcome of adolescents and adults with iGCT. Methods: Data were collected from 10 institutions in Germany and Switzerland. Pts aged >/= 16 years at first diagnosis or at relapse with a primary iGCT were included. Objective responses were evaluated by local investigators. Statistics (Cox proportional hazard model, progression-free survival (PFS) and overall survival (OS) analyzed by Kaplan-Meier method) were performed with SPSS v29. Results: We identified 75 pts (92.0% male) with a median age of 23 years (range 16-60, 94.7% >/= 18 years). At first diagnosis, histology was pure germinoma in 70.7%, pure teratoma in 10.7%, other non-germinomatous GCT (NGGCT) in 13.3%, unknown in 5.3% of pts. Localized, bifocal, and metastatic disease was found in 72.0, 6.7, and 21.3% of pts. As part of their first line (1L) treatment, 69.3%, 80.0%, and 62.7% received surgery, radiotherapy, and chemotherapy, respectively. High dose chemotherapy/ autologous stem cell transplantation (HDCT/ASCT) was part of 1L treatment in n=3 pts with NGGCT. Trimodal and bimodal treatment was performed in 48.0% and 32.0% of pts. Response to 1L therapy was complete remission (CR) in 61.3%, partial remission tumor marker negative (PRm-) in 16.0%, PRm+ in 4.0%, PR with tumor marker status unknown in 4.0%, progressive disease (PD) in 2.7%, and unknown in 12.0%. Relapse occurred in 13/75 pts (17.3%) with unknown histology (n=4), teratoma (n=2), other NGGCT (n=4), and germinoma (n=3). In 2 pts. in whom germinoma was diagnosed at time of first diagnosis, at time of recurrence PNET and Yolk sac tumor were histologically proven. Median time to relapse was 19.0 months (mo.; range 3-223). HDCT/ASCT as salvage treatment was performed in 5 pts with NGGCT and in one pt with germinoma as 2L (n=5) or 3L (n=1). NGGCT histology was associated with increased risk for recurrence or death (p=0.012 and 0.039).3-year PFS was 90.7% (germinoma: 98.1%, NGGCT: 73.9%) and 5-year OS was 92.0% (germinoma: 98.1%; NGGCT: 78.3%). Median follow-up time was 60 mo (range 0-339). Conclusions: Disease characteristics, treatment and outcomes of adolescent/ adult iGCT pts are comparable to those reported in pediatric pts. High cure rates are achieved in pts with pure germinoma and current treatment concepts. In pts with NGGCT further investigation is needed to improve survival outcomes.