Background: The management of a Stage I immature teratoma during pregnancy with a review of the literature is reported. Case Report: A growing adnexal mass was removed at 12 weeks of gestation. Although the frozen section was negative, because of intraoperative clinical suspicion, a right salpingo-oophorectomy and surgical staging were performed. Histological examination revealed a Stage Ia, grade 1 immature ovarian teratoma. Appropriate surgical staging enabled avoidance of chemotherapy despite the unexpected histological diagnosis. The pregnancy was terminated because of fetal distress, with cesarean section at 34 weeks of gestation. At that time the peritoneal cavity was inspected and biopsies were taken as in second-look laparotomy. Two years after the first operation the patient remains disease free. Conclusion: For adnexal masses removed during pregnancy frozen section is useful but when there is clinical suspicion surgical staging must be performed.