We described a case of Dandy-Walker syndrome, that was detected in utero and was evaluated and monitored postnatally. The prenatal examination by echography and MRI revealed a large posterior fossa cyst with splaying of the cerebellar hemispheres. The male infant was born at 40 weeks of gestation, weighing 3430g with no special problems. Although the infant presented transient tachypnea immediately after birth, he has had no neurological symptoms. Echography, computed tomography (CT) and magnetic resonance imaging (MRI) performed after birth revealed an enlargement of the fourth ventricle but not of the lateral ventricles, and dysgenesis of the cerebellar vermis. Circumference of the head was normal and no extracranial anomalies except for the left simian crease were noted. Chromosomal analysis showed normal male pattern, 46,XY. He has been carefully followed up with no neurosurgical treatment. He has showed normal growth and development, and no hydrocephalus, as of 3 months of his age.