Sacrococcygeal teratomas have been diagnosed prenatally on sonograms as masses of cystic, solid, or mixed echogenicity from the sacral area and protruding through the perineum or buttocks. However, a cystic sacrococcygeal teratoma may be misdiagnosed as an anterior sacral meningomyelocele, especially when presenting as a posterior cystic mass. We report a case in which three-dimensional power Doppler imaging was helpful for making a correct prenatal diagnosis of a type 1 cystic sacrococcygeal teratoma, which mimicked a meningomyelocele.