Pallister-Killian syndrome (PKS), which is characterized by mental retardation, seizures, pigmentary skin lesions and dysmorphic facial features, is a rare chromosomal anomaly with the mosaic presence of an extra tissue-specific isochromosome 12p (mosaic tetrasomy 12p). Advanced maternal age is believed to be a risk factor for PKS. Ultrasound is a useful tool in the prenatal detection of characteristic findings associated with PKS. This article provides an overview of the prenatal sonographic features of PKS, including congenital diaphragmatic hernia, polyhydramnios, abnormal extremities, increased nuchal translucency or nuchal edema, cardiovascular anomalies, central nervous system anomalies, an abnormal facial profile, and other rare anomalies. Appropriate tissue samples and laboratory analytic techniques should be selected for an accurate prenatal diagnosis because of the instability of isochromosome 12p and the potentially incorrect interpretation as tetrasomy 21q on the traditional G-banded technique. Fryns syndrome, which has phenotypic overlap with PKS, is also discussed. Increasing awareness and knowledge of various anomalies of PKS on prenatal ultrasound would be helpful for the early detection of PKS. Definite diagnosis of fetuses with PKS could help clinical physicians in the decisionmaking process during the prenatal or postnatal periods.