Trachael diverticulum is a very rare anomaly of the trachea. Among them are recognized estenosis, tracheomalacia, tracheal membranes and tracheoesphagic fistula. Until our case, there has been no existence of a publication of this prenatal diagnosis. Due to the poor incidence of pathology and to the diversity of results found, there is no protocol of management for this type of pathology. A 29-year-old primipara was referred to our center at 29 weeks' gestation with diagnosis of polyhydramnios. Fetal biometric measurements were on the 50th percentile. In our ultrasound we found an upper neck cyst, centrally localized without vascularization. The cyst displaced the trachea. With 3D multiplanar technique, we made the anatomical correlations. The diagnosis was confirmed in the postnatal period with multislice CT. We show the prenatal ultrasound images in 2D ultrasound and 3D multiplanar technique with postnatal correlation. To our knowledge, this is the first reported case of antenatal diagnosis of tracheal diverticulum.