We describe a rare case of primary cardiac lymphoma associated with complete atrioventricular block, with recovery following systemic chemotherapy. A 61 year-old woman was admitted because of a massive pericardial effusion and complete atrioventricular block. Echocardiography disclosed several polypoid masses in the right atrium. A diagnosis of primary cardiac lymphoma was made. After three cycles of chemotherapy, the patient achieved a complete remission, the ECG showed first-degree atrioventricular block, and echocardiography revealed disappearance of the right atrial masses. This is the first report of a patient recovering from primary cardiac lymphoma and complete atrioventricular block following systemic chemotherapy. We conclude that aggressive treatment of this malignancy can improve cardiac function and the patient’s prognosis.