Cebocephaly is an exceedingly rare malformation of the face characterized by a single-nostril nose, occurring with an estimated incidence of 1/40,000 deliveries. It is always associated with holoprosencephaly (HPE) and, as such, is also associated with a high risk of chromosomal abnormalities and other genetic conditions. The prenatal diagnosis of cebocephaly can be made by ultrasound during the second and third trimesters, and it often results from a focused examination of the fetal face following the detection of HPE. Nevertheless, the diagnosis is frequently overlooked, as the views required for showing the single nostril are sometimes difficult to obtain due to the associated small size of the abnormal fetal nose and the flexed position of the head. Two cases of cebocephaly detected by transabdominal ultrasound at 27 and 16 weeks’ gestation are presented to illustrate the prenatal features. Both were associated with a chromosomal abnormality, partial deletion 18p in one and trisomy 13 in the other. The facial features associated with HPE are also briefly reviewed.