Background: Malignant sex cord-stromal cell tumours (SCST) account for only 7% of ovarian malignancies. The Arbeitsgemeinschaft fuer Gynaekologische Onkologie (AGO) study group has established a clinicopathological database to provide an overview of the current treatment strategies and survival of SCST patients and to identify research needs. Methods: Twenty centres provided mixed retro- and prospective data of patients with tumour specimens and second-opinion pathology review treated between 2000 and 2014. Descriptive analyses of treatment strategies, Kaplan–Meier curves and cox regression analyses were conducted. Results: Two hundred and sixty-two SCST patients were included. One hundred and ninety-one Granulosa-cell tumour (GCT) and 17 Sertoli-Leydig cell tumour (SLCT) patients were stage I disease (>80%). Forty four GCT (18.7%) and two (8.3%) SLCT patients received adjuvant systemic treatment. After a median observation time of 78.2 months, 46% of all SCST patients experienced disease recurrence, treated predominantly with secondary debulking surgery (> 90%). Advanced FIGO stage, lymph node involvement and intra-operative capsule rupture were associated with disease recurrence on univariate analysis (all p < 0.05). Median OS time was not reached. Discussion: In this analysis of SCST patients, adjuvant chemotherapy was unable to prevent disease recurrence. Despite high recurrence rates, overall survival rates were excellent.