The eustachian valve, or valve of the inferior vena cava, is an embryogenic derivative of the right valve of the sinus venosus. Although it generally disappears during fetal life, its persistence may simulate symptoms of cardiac disease, particularly those associated with atrial tumors. We describe a case of prenatal diagnosis of a persistent, large and prominent eustachian valve with redundant tissue attached to the junction of the inferior vena cava and the right atrium. The neonate was asymptomatic and was healthy at 7 months of age at the time of writing. This is the first time that this finding has been diagnosed prenatally.