A case of intestinal angiocentric T/NK-cell lymphoma in a 58-year-old man is reported. The patient presented initially with panperitonitis because of perforation of sigmoid colon diverticulum. He underwent segmentectomy of involved bowel. Histologically, the intestinal wall showed diffuse infiltration of medium or large size lymphoma cells with angiocentric growth and necrosis. The lymphoma cells were CD56+, CD45RO+, CD3+, CD4-, CD8-, CD20-, and CD30- in paraffin sections with germline configuration of TCR-γ gene, consistent with T/NK-cell lymphoma. Further staging revealed splenomegaly. Intestinal angiocentric T/NK cell lymphoma represents a distinct etiology of diverticulum with perforation.