Primary hepatic lymphoma is a rare disorder representing less than 1% of all extranodal lymphomas. Histological examination of a primary hepatic lymphoma usually reveals a diffuse large B-cell lymphoma; there have been few reports of primary hepatic mucosa-associated lymphoid tissue (MALT) lymphomas. A 67-year-old man was being treated for a duodenal ulcer; while receiving therapy for the ulcer, a liver mass was incidentally found on abdominal ultrasonography. The pathologic diagnosis of the hepatic mass was an extranodal marginal zone B-cell lymphoma of MALT. The patient underwent radiotherapy with a total of 4,140 cGy delivered. The patient achieved complete remission and has been followed for 6 years with no recurrence of the disease. This report reviews the case of a primary hepatic extranodal marginal zone B-cell lymphoma of MALT successfully treated by radiotherapy alone.