Background: Characteristics and outcome of non-seminomatous testicular germ cell tumours (NSGCT) with teratoma-containing primaries are still under debate. Methods: We performed a retrospective analysis including 557 patients with metastatic NSGCT as a registry study within the "German Testicular Cancer Study Group". Results: Of the eligible 557 patients with NSGCT, 237 (42%) of all orchiectomy specimens had teratoma-containing primaries, while 320 (58%) were teratoma-free. Teratoma-containing primaries had a significantly higher clinical stage (p=0.002) and worse prognosis (p=0.051) compared to teratoma-free specimens. Lymph node metastasis were significantly larger before (4.5 vs 2.5cm; p<0.001) and after chemotherapy (3.5 vs 2.5 cm; p<0.001) in teratoma-containing primaries. Post-chemotherapy retroperitoneal lymph node dissection was performed in 57% of all patients. As teratoma-containing specimens revealed a significantly lower number of complete responses after chemotherapy, PC-PRLND was more often performed, with teratomatous elements being more often present in the PC-RPLND specimens compared to non-teratoma containing primaries. Kaplan-Meier estimates revealed that 19% of all patients relapsed during a median follow-up of 56 months [29-112] with a median time to relapse of 10 months. Teratoma-containing had a significantly lower relapse-free survival (RFS) compared to teratoma-free NSGCT (relapse rate 24% vs 16%, p=0.020). 8% (45/533) of all patients died due to their disease. There was no difference regarding the tumour-specific survival between teratoma-containing NSGCT and teratoma-free NSGCT when looking at the entire cohort of patients (8% vs. 9%, p=0.563), however median overall survival was not reached. Conclusions: In our study, NSGCT patients with teratoma-containing primaries showed a significantly higher clinical stage and worse prognosis at time of presentation compared to teratoma-free primaries. Furthermore, patients with teratoma-containing primaries showed a significantly worse relapse-free survival. Consequently, treating physicians should be aware of these patients portending a dismal prognosis and the presence of teratomatous elements might act as a reliable stratification tool for treatment decision in TGCT patients.