Background:　Primary　lymphomas　of　the　heart　are　very　rare,　especially　primary　cardiac　extranodal　natural　killer/T-cell　Lymphoma.　Primary　cardiac　natural　killer/T-cell　lymphoma　has　diversified　symptoms　and　the　diagnosis　is　difficult.　Case　presentation:　We　have　reported　a　35　year　old　man　with　palpitation,　fever　and　increasing　dyspnea.　Transthoracic　echocardiography　was　done　and　showed　a　large　piece　of　mass.　We　resected　the　mass　which　was　in　the　right　atrium.　Pathologic　examination　of　removed　cardiac　tumor　had　reported　as　below:　non　Hodgkin-NK/T　cell　lymphoma.　The　patient　received　surgery,　without　chemotherapy,　and　was　died　on　the　27th　day　after　surgery　of　follow-up.　Conclusion:　This　disease　has　a　quick　progression　and　a　poor　prognosis.　Only　surgery　couldn＇t　control　primary　cardiac　natural　killer/T-cell　Lymphoma　very　well.　Therefore,　early　detection　is　becoming　more　important.