A two and a half year old child was admitted to hospital with peripheral cyanosis. Echocardiography revealed severe dilated cardiomyopathy affecting both ventricles with abnormally hypertrophied and irregular myocardial walls. The pulmonary hypertension was suprasystemic with raised pulmonary resistances. The magnetic resonance imaging and angiography confirmed the diagnosis of persistence of spongy myocardium. This is a rare abnormality due to the persistence of embryonic myocardium with a network of trabeculations and intertrabecular spaces as usually observed during echocardiography. This case is noteworthy because of the biventricular involvement and the absence of associated congenital cardiac malformation. The prognosis is characterised by a high risk of severe cardiovascular complications.