Natural Killer cell lymphoma pursued a highly aggressive clinical course, with the aggressiveness and poor prognosis in this biologically distinct primary gastrointestinal lymphoma, a more vigorous systemic therapy should be considered in the addition to surgery. We report an unusual case of aggressive primary Natural Killer cell (NK cell) lymphoma of the cecum. A 38-year old man admitted for intractable fever, diarrhea, and hematochezia. The patient diagnosed as primary NK cell cecal lymphoma with perforation after surgical resection. The primary lesion was deep ulceration with perforation and it revealed metastasis to liver. The immunophenotype of the tumor cell were CD56+, CD3+, UCHL-1+, CD45RO+, polyclonal IGH, TCRr, so confirmed NK cell type lymphoma.