Williams syndrome (WS) is a genetic disorder due to deficiency of elastin gene expression. It is characterized by typical somatic abnormalities and a wide range of cardiovascular malformations. Coronary artery involvement is a frequent finding of the syndrome, particularly in those patients with severe supravalvular aortic stenosis. We present the case of an 11-month-old infant affected by WS who developed severe coronary artery disease 2 months after the surgical repair of supravalvular aortic stenosis. The clinical picture and successful surgical revascularization strategy is also described.