To report a rare presentation of bilateral endometriomas in an adolescent and describe characteristics of endometriomas.Case report.Major academic medical center.An 18-year-old G0 presented with an incidentally found 35-cm pelvic mass that was found to be bilateral endometriomas.Exploratory laparotomy with resection of endometrioma cyst walls and lysis of adhesions.The incidence, pathogenesis, fertility implications, and treatment options for endometriomas in adolescents.Endometriomas are rare in adolescents. There are no case reports in the literature to date.Endometriosis should be considered in adolescents presenting with bilateral complex ovarian masses regardless of their size.