Galen vein aneurysm is a rare congenital malformation, occasionally detected on antenatal ultrasound scans as an anechoic structure in the midline posteriorly of the brain with prominent color flow Doppler. It consists of multiple feeding arteries, principally the anterior and posterior choroidal arteries and the anterior cerebral artery. May be associated with congenital heart disease, hydrops, and cystic hygroma. Because a Galen vein aneurysm has a low incidence rate, but high morbidity and mortality rates, a prenatal diagnosis is necessary for adequate follow-up, delivery, and parent counseling. Echocardiogram and fetal resonance can be important complementary imaging exams.