Primary cardiac lymphoma (PCL) is a rare subset of non-Hodgkin's lymphoma involving the heart and/or pericardium with no or minimal evidence of extracardiac involvement at presentation. Distant relapses have infrequently been observed. We report two cases of this disorder that showed isolated central nervous system (CNS) relapse. Diagnosis by endomyocardial biopsy was consistent with diffuse large B-cell lymphoma. After immunochemotherapy they achieved complete remission (CR). Eight and five weeks after, isolated CNS relapses were observed respectively. The first patient was treated with high-dose methotrexate (HD-MTX) and high-dose cytarabine, resulting in a second CR. She then went onto receive autologous stem-cell transplantation but unfortunately died shortly after because of infection. The second patient received systemic CNS prophylaxis with HD-MTX, and later she was treated with an induction chemotherapy strategy with evidencing of progressive disease after two courses of treatment. She was subsequently initiated on a salvage therapy with cytarabine, followed by whole-brain radiotherapy, and autologous stem-cell transplant (ASCT), finally achieving a complete remission. Isolated CNS relapse is a very uncommon pattern in PCL and a standard approach to treatment is not yet well established. Nevertheless, the importance of CNS evaluation, using magnetic resonance imaging (MRI) and lumbar puncture, in patients with PCL should be considered, and further studies are recommended to determine the appropriate management of this complication.