Cardiac complications of the pediatric patients with acute leukemia are common. Most of the cardiac complications may be due to chemotherapeutics such as antracyclins, besides anemia, infections, or direct leukemic infiltrations of the heart. It is reported that leukemic infiltration is frequent in the postmortem examination of the myocardium and pericardium. However, at the antemortem examination, pericardial involvement is rare and there is no myocardial involvement reported at the time of diagnosis in patients with acute leukemia in the English literature. Here, the authors report an adolescent with acute lymphoblastic leukemia who had myocardial infiltration at the time of diagnosis.