Hemivertebrae is the most common form of congenital scoliosis, although the overall prevalence is rare. We report a 28-year-old primigravida who sought evaluation at our institution for spinal deformity at 21 weeks gestation. Using two- and three-dimensional ultrasonogaphy, an abnormal shaped thoracic vertebra with a missing rib, deviated alignment, and scoliosis was demonstrated in the fetus. After delivery due to premature rupture of membranes, an infantogram confirmed a single hemivertebra at T11, which was in agreement with the prenatal sonographic findings. Here we discuss the value of three-dimensional ultrasonography as an essential diagnostic tool for the prenatal diagnosis of a hemivertebra.