OBJECTIVE: To examine the association between ovarian conservation and oncologic outcome in surgically-treated young women with early-stage, low-grade endometrial cancer. METHODS: This multicenter retrospective study examined women aged <50 with stage I grade 1-2 endometrioid endometrial cancer who underwent primary surgery with hysterectomy from 2000 to 2014 (US cohort n = 1196, and Japan cohort n = 495). Recurrence patterns, survival, and the presence of a metachronous secondary malignancy were assessed based on ovarian conservation versus oophorectomy. RESULTS: During the study period, the ovarian conservation rate significantly increased in the US cohort from 5.4% to 16.4% (P = 0.020) whereas the rate was unchanged in the Japan cohort (6.3-8.7%, P = 0.787). In the US cohort, ovarian conservation was not associated with disease-free survival (hazard ratio [HR] 0.829, 95% confidence interval [CI] 0.188-3.663, P = 0.805), overall survival (HR not estimated, P = 0.981), or metachronous secondary malignancy (HR 1.787, 95% CI 0.603-5.295, P = 0.295). In the Japan cohort, ovarian conservation was associated with decreased disease-free survival (HR 5.214, 95% CI 1.557-17.464, P = 0.007) and an increased risk of a metachronous secondary malignancy, particularly ovarian cancer (HR 7.119, 95% CI 1.349-37.554, P = 0.021), but was not associated with overall survival (HR not estimated, P = 0.987). Ovarian recurrence or metachronous secondary ovarian cancer occurred after a median time of 5.9 years, and all cases were salvaged. CONCLUSION: Our study suggests that adoption of ovarian conservation in young women with early-stage low-grade endometrial cancer varies by population. Ovarian conservation for young women with early-stage, low-grade endometrial cancer may be potentially associated with increased risks of ovarian recurrence or metachronous secondary ovarian cancer in certain populations; nevertheless, ovarian conservation did not negatively impact overall survival.