Hepatosplenic T-cell lymphoma is a rare histologic type of peripheral T-cell lymphoma that usually presents with hepatosplenomegaly, B-symptoms, and often with rapid and aggressive progression. There have been no previous domestic reports of a hepatosplenic T-cell lymphoma involving the colon. We report a case of a 61-year old man with colonic invasion of a hepatosplenic T-cell lymphoma. He presented the sudden onset of fever accompanied by severe pancytopenia and rapid liver enzyme elevation without evidence of lymphadenopathy. Multiple tiny erosions were noted during colonoscopy. In addition, many immature lymphocytes with vague nucleoli, abundant eosinophilic cytosol, and nuclei of small-to-medium size were seen within the sinusoids on liver biopsy. A similar pattern existed on colonic mucosa obtained from colonoscopic biopsy. Thus, with the aid of such a specific clinical presentation and the results of immunohistochemical staining, we made a definitive diagnosis of hepatosplenic T-cell lymphoma with colonic involvement.