A 2-month-old infant with congestive heart failure was referred to the authors’ hospital. Echocardiography exhibited a dilated left ventricle (LV), poor LV systolic function, and intraventricular thrombus. Laboratory data showed a normal creatinine phosphokinase level and negative troponin T test results. The congestive heart failure was managed using a beta-blocker, an angiotensin receptor blocker, and diuretics. Head computed tomography performed during the treatment course showed periventricular calcifications. Congenital cytomegalovirus infection was subsequently diagnosed. Fetal echocardiography performed during pregnancy showed impaired LV function, suggesting that the cardiomyopathy was associated with cytomegalovirus infection in utero.