The vein of Galen aneurysmal malformation (VGAM) is a rare cerebral arteriovenous shunt, which may be associated with a congenital cardiac defect. Embolisation of the VGAM may be undertaken in the neonatal period if necessary, but is safer in infancy. Recent advances in neuroradiology have changed the prognosis for this group with many patients achieving survival with normal development. This case report describes a patient with a sinus venosus defect (SVD) and a VGAM and considers both the optimal timing of treatment of the two malformations and the conduct of anaesthesia for open repair of the SVD in the presence of an untreated VGAM.