Laparoscopic approaches to giant ovarian cysts, particularly in adolescents, have critical management concerns as follows: risk of malignancy, risk of cyst rupture, and limited working space. A 15-year-old girl presented with a giant (>25 cm) ovarian serous cyst adenoma containing 7 L of fluid. At open laparoscopy, a giant, entirely cystic, smooth mass originating from the right ovary and lying between the symphysis and the xiphoid was observed. After intraabdominal fluid aspiration, open conservative cystectomy was performed, avoiding spillage. The patient made an uneventful postoperative recovery and was discharged on the second postoperative day. To our knowledge, this is the largest ovarian cyst treated conservatively in an adolescent. Minimal access surgery, laparoscopy and open cystectomy, can be safely proposed in this group of patients. Conservative surgery should always be evaluated for preservation of ovarian function in cases of giant ovarian cysts in adolescents.