Noncompaction of the ventricular myocardium is a rare congenital cardiomyopathy resulting from an arrest in normal endomyocardial embryogenesis. This disease is characterized by numerous and prominent trabeculations and deep intertrabecular recesses. It may be isolated or associated with other congenital heart diseases. The disorder is clinically accompanied by depressed ventricular function, systemic embolization and arrhythmias. Sustained bradycardia is infrequent in prenatal life and associated with maternal collagen vascular diseases, structural heart diseases or long QT syndrome. Herein we report a case of isolated noncompaction of left ventricular myocardium diagnosed in the first day of life and followed previously by serial fetal echocardiograms for the sustained sinus bradycardia. On postnatal electrocardiography, there was junctional escape rhythm due to profound sinus bradycardia, leading us to consider sick sinus syndrome. To our knowledge, this is the first case in the literature of isolated noncompaction of left ventricular myocardium with sustained bradycardia due to sick sinus syndrome.