We present a case of a fetal lumbar myelocystocele, a rare congenital malformation, characterized by herniation of the central canal through a bony spina bifida. Routine ultrasound examination at 11 weeks' gestation by the primary obstetrician showed a suspicious cyst on the fetal back. Initially, the suspected diagnosis was a meningocele. After sonographic detection of newly developed fetal brain anomalies at 22 weeks' gestation the patient was referred to us. The enlarged cyst, which floated freely in the amniotic fluid, had a funnel-like appearance and was covered by a very thin layer of skin. With the help of ultrafast fetal magnetic resonance imaging the diagnosis of a fetal myelocystocele was made.