The aim of the present study was to evaluate the oncologic safety and reproductive outcome in patients with stage I epithelial ovarian cancer (EOC) treated with fertility-sparing surgery (FSS). Women aged ≤40 years with stage I EOC who had undergone FSS between 2000 and 2010 were retrospectively reviewed. Survival was examined using the Kaplan-Meier method and statistical significance was analyzed using the log-rank test. A total of 29 EOC patients (stage IA, n=14; stage IC1 n=6; stage IC3, n=9) from seven participating institutions belonging to the Tohoku Gynecologic Cancer Unit were enrolled. After a median follow-up duration of 60.6 months (range, 6-135 months), five patients (17.2%) experienced tumor recurrence. The respective five-year relapse-free survival (RFS) and overall survival (OS) rates were 90.9 and 100% for stage IA/IC1, and 43.8 and 87.5% for stage IC3. Significant differences in RFS were observed between stage IA/IC1 and IC3 patients (P=0.026). However, there was no significant difference in OS between patients with 1A/1C1 and those with 1C3 (P=0.712). After FSS, seven pregnancies occurred in five patients, which resulted in the birth of six healthy children. The results of the present study confirmed that FSS may be an acceptable treatment method for stage IA and IC1 EOC, exhibiting a favorable reproductive outcome. However, the safety of FSS for treating stage IC3 EOC is uncertain and warrants further investigation.