Hypoplastic left heart syndrome is a congenital heart disease which accounts for 8% of all congenital heart defects. Twin pregnancies have a significantly higher risk of structural heart disease than singleton ones, however the concordance rate has been found to be relatively low, even in monochorionic pregnancies. We describe here the favorable evolution of a monochorionic, diamniotic, twin pregnancy in which both fetuses were diagnosed with hypoplastic left heart syndrome by antenatal echocardiography. The present report suggests that at least in some cases there may be a genetic contribution to the etiology. The fetal diagnosis was imperative to a good postnatal outcome.