Mediastinal neurenteric cysts are the least common types of the bronchopulmonary foregut malformations, and their antenatal diagnosis is rare. We report a case of mediastinal neurenteric cyst diagnosed on antenatal ultrasonography at 28 weeks' gestation. A small intraspinal component and vertebral segmentation anomalies were also noted. The diagnosis was confirmed on postnatal magnetic resonance imaging and at the time of operation.