T-cell-rich B-cell lymphoma (TCRBCL) is an uncommon and recently recognized variant of B-cell non-Hodgkin lymphoma characterized by a few large neoplastic B cells amid a predominant population of reactive T lymphocytes and variable numbers of histiocytes. Morphologically, TCRBCL resembles a variety of non-Hodgkin lymphomas and Hodgkin disease. Accurate diagnosis and proper treatment are essential to assure a favorable prognosis. To our knowledge, this is the first report of ethmoid sinus presentation of TCRBCL in an Epstein-Barr virus-negative 51-year-old man. Combined chemotherapy and radiotherapy were administered based on the correct diagnosis. The patient has had a complete response with no recurrence during the 5-year follow-up.