A 14-year-old female patient consulted due to 4 months of recurrent right pelvic pain during her menstrual period. Sonography revealed a 35 mm haemorrhagic right ovarian cyst, initially treated with hormone therapy and oral analgesics with no response. Surgery was indicated due to growth on sonography control and no response to medical treatment. Laparoscopy showed a 7 cm leiomyomatous-like mass arising from the right round ligament that was extracted en bloc without rupture with right salpingectomy and ovarian preservation. The histopathological examination confirmed the diagnosis of round ligament endometrioma with no atypia. The patient presented an uncomplicated postoperative course and was discharged home 48 hours after surgery. Hormonal contraceptives were initiated after the histopathological confirmation; the patient remains asymptomatic at 1-year follow-up.