Primary cardiac tumors are exceedingly rare with variable clinical manifestations. This case involves a patient presentation of symptomatic complete heart block and cardiac imaging revealing a right atrial mass invading the myocardium consistent with Burkitt lymphoma on histopathology. The patient received definitive bradytherapy with a pacemaker and chemotherapy for the primary cardiac lymphoma. After three cycles of chemotherapy, the right atrial mass regressed significantly with restoration of atrioventricular conduction and no pacing burden. Primary cardiac lymphomas infrequently manifest as atrioventricular block and this case highlights cardiac masses as a potential etiology when evaluating new conduction disturbances and bradyarrhythmias.