We report a case of primary diffuse large B-cell lymphoma of the prostate in a 54-year-old Caucasian male who presented with urinary retention and benign prostatic hyperplasia. We discuss the rare presentation of this disease and its clinicopathologic features and review the literature for up-to-date information on the diagnosis and clinical management. Despite the low incidence of lymphoma involving the prostate gland, it should always be considered as part of the differential diagnosis in cases of prostate gland enlargement with urinary tract obstructive symptoms resistant to medical therapy. Treatment modalities for this rare disease are also discussed.