Background: The treatment of heart failure has changed with the use of angiotensin converting enzyme inhibitors (ACEIs) and beta-blockers since the middle of the 1990’s. However, the outcome in infantile dilated cardiomyopathy… (DCM) when treated with them remains poorly understood. Methods: We reviewed the medical records of infants with DCM within 24 months old in our hospital between 1979 and 2012, and compared the outcome in the later group (1997-2012) with that in the early group (1979-1996). The survival and cardiac event (CE) free survival rates were calculated by the Kaplan–Meier method. Results: There were 20 patients in the early group and 24 patients in the later group. The median left ventricular fractional shortening at the onset of disease in the early and later groups were 11% (range 4-17) and 12% (range 4-25), respectively. In the later group, ACEIs and beta-blockers were administered in 22 and 21 patients, respectively. An usual low dose induction of carvedilol therapy (0.01-0.02mg/kg/day) sometimes worsened the heart failure in 9 patients (43%) after the successful initial conventional treatment for acute heart failure. Nineteen patients died and 25 survived. The CEs were as follows: heart transplantation 4, mitral valvuloplasty 1, Batista operation with mitral valve replacement 1, and cardiac resynchronization therapy in the late period 1. The 20-year survival rate in the early and later groups were 5% (95%CI 0.7-28) and 100%, respectively (p<0.001). The 2-year CE free survival rate in the early and later groups were 5% (95%CI 0.7-28) and 83% (95%CI 59-91), respectively (p<0.001). Conclusions: The outcome in patients with infantile DCM has significantly improved with careful acute and chronic treatments using ACEs and beta-blockers since the 2000’s. Adopting a long-term supportive treatment during a period of low ventricular function and the use of beta-blockers corresponding to each patient’s condition were key to survival.