Background: Juvenile granulosa cell tumors (JGCT) are rare sex cord-stromal tumors which occur primarily in children and adolescents. Methods: All individuals or proxy caregivers provided informed consent/assent for participation in the International OTST Registry. Clinical data was collected. When available, pathology was centrally reviewed. Staging was evaluated using the International Federation of Gynecology and Obstetrics (FIGO) classification. Kaplan-Meier survival analyses and exact permutation tests were performed. Results: Forty-two individuals with ovarian JGCT were enrolled. Median age at diagnosis was 9 years (range 0-27). Most individuals had Stage I disease (Stage Ia=16; Stage Ib=1; Stage Ic=16). Seven individuals presented with higher stage (Stage II=2; Stage III=5). Stage was unknown for 2 individuals. Three-year overall survival (OS) was 88% (CI 77%, 100%) and event-free survival (EFS) was 69% (CI 54%, 88%). At median follow-up time of 25 months (range 0-416), 9 patients (Stage Ia=1, Stage Ic=5, Stage III=3) had recurrent disease. Use of post-operative adjuvant chemotherapy varied by stage and timing of rupture. Of those with Stage Ic JGCT, 2/7 with preoperative rupture and 3/9 with intraoperative rupture recurred. Among individuals with recurrence, median time to recurrence was 11.5 months (range 3-19). Four of 9 individuals with recurrence survived (no evidence of disease n=2; alive with disease n=2). All individuals who died presented with extrapelvic recurrence. Median time from recurrence to death was 10 months (range 2-53). In individuals with recurrence, advanced stage at diagnosis (HR 5.1; p-value 0.087) and recurrence outside the tumor bed (HR Infinity; p-value 0.048) were associated with inferior OS. Three-year OS for individuals with recurrence was 57% (CI 30%, 100%). Conclusions: Low stage JGCT is associated with a favorable prognosis, however, recurrence is associated with lower survival rate. Within this series, recurrences presented within 2 years of diagnosis. Novel strategies are needed to address recurrent and extrapelvic disease.