Cardiac resynchronization therapy (CRT) is proved to prevent heart transplantation in some patients with dilated cardiomyopathy and mechanical dyssynchrony. We report of the benefit of CRT accomplished by atrial synchronized single-site left ventricular pacing in an 8-year-old boy with idiopathic dilated cardiomyopathy, normal atrioventricular conduction, borderline QRS complex duration (120 ms), and marked mechanical left ventricular dyssynchrony proved by echocardiographic speckle tracking.