A primary small intestinal natural killer (NK) cell lymphoma with pathologic features of enteropathy but lack of association with celiac disease is reported. A 37-year-old man presented with tarry stool, coffee-ground vomitus, and mild fever. He did not have chronic diarrhea or malabsorption. Segmental resection of the duodenum and jejunum showed multicentric transmural infiltration by medium-sized lymphoma cells expressing CD3, CD8, cytotoxic granules, and Epstein-Barr virus by in situ hybridization. The nontumorous mucosa away from the main tumor revealed enteropathy with villous blunting and increased intraepithelial lymphocytes sharing the same immunophenotype as the lymphoma cells. Both lymphoma and nontumorous areas were germline for T-cell receptor-gamma and immunoglobulin heavy chain gene rearrangement. Serologic test by ELISA was negative for anti-transglutaminase. The patient died of repeated gastrointestinal bleeding and sepsis at 2 months. Differential diagnosis of this unique nasal-type NK-cell lymphoma with enteropathy-associated T-cell lymphoma is discussed.