We report the case of a 17-year-old man with precursor B-lymphoblastic lymphoma involving an intracardiac mass and myocardial infiltration. Intensified chemotherapy followed by autologous peripheral blood stem cell transplantation resulted in long-term complete remission for over 5 years. As the most frequent sites of B-lymphoblastic lymphoma involvement are the skin, soft tissue, bone, and lymph nodes, reports of cases harboring cardiac involvement are relatively few. This is a rare case of B-lymphoblastic lymphoma displaying cardiac involvement, in which cardiac infiltration was one of the initial manifestations.