We report a series of 9 children with neonatal Marfan syndrome. The diagnosis was made on a striking facial dysmorphia associated with arachnodactyly type skeletal anomalies. They all had cardiovascular anomalies: aortic dilatation 9 times, and mitral and/or tricuspid valve prolapse 8 times. Three children underwent ascending aorta replacement with the Yacoub technique. There was one operative death in a young infant and the two survivors required further surgery for gross mitral insufficiency and an aneurysm of the horizontal aorta. Three children died before the age of 1 year from cardiac insufficiency linked to massive leaks of all the valves. The three youngest children in the series did not undergo any procedure and were followed up for a slowly growing dilatation of the initial aorta. The prognosis of neonatal Marfan syndrome is weighted with a heavy mortality. The timing of surgical intervention in case of excessive dilatation of the aortic root is difficult to determine. It depends not only on the aortic diameter but also on the aortic valve function and the existence of other mitral or tricuspid lesions. Surgical treatment for lesions of the initial aorta and the atrioventricular valves improves the short-term prognosis but the risk of re-intervention is higher.