The majority of abdominal masses detected in the neonatal period are benign (85%) and usually originate in the urinary tract (50%), genital system (15%), gastrointestinal system (15%), or the hepatobiliary tract (5%). Ovarian cysts comprise one-third of the masses with a genital origin. Presently described is a case of an ovarian cyst that developed during the antenatal period and transformed into a hemorrhagic cystic mass as a result of torsion. A female infant born at 37 weeks of gestation with the prediagnosis of nephroma was admitted to the neonatal intensive care unit. Abdominal ultrasonography revealed a smooth cystic mass approximately 50x45x35 mm in size in the left upper quadrant that was not associated with the kidney. Magnetic resonance imaging revealed a 55x44x49-mm cystic mass in the left adnexal region containing multiple septations that were not enhanced with contrast material, and the mass was then interpreted as a hemorrhagic fetal ovarian cyst. The left ovary, compromised by 2 full torsions, was removed during a laparoscopy performed on the postnatal seventh day. The infant was subsequently discharged without complications. It should be kept in mind that cystic masses detected in the prenatal period may be of ovarian origin. An appropriate follow-up and treatment should be planned according to the size of the ovarian cyst and the clinical findings.