A 1.8-year-old male required a conventional DDD pacemaker for an atrioventricular block after congenital heart surgery. Five years later, heart failure due to left ventricular (LV) dyssynchrony progressed and we performed cardiac resynchronization therapy (CRT). Long-term echocardiographic follow-up showed that LV shortening fraction had improved within the first year after CRT, and LV end diastolic dimension had decreased after the first year. During LV remodeling (1-24 months after CRT), the QRS duration shortened without a change in the JT and Tpeak-end interval. The New York Heart Association class improved from III to I during the 2.3-year follow-up.