Although secondary renal involvement from systemic lymphoma is common, primary renal lymphoma (PRL) is a rare disease. PRL is defined as a non-Hodgkin's lymphoma arising in the renal parenchyma and not resulting from invasion of an adjacent lymphomatous mass. The overall prognosis for PRL is poor. We report a case of a 58-year-old man who presented with right flank pain and underwent radical nephrectomy with the presumptive diagnosis of renal cell carcinoma. The pathological examination of the tumor revealed diffuse large B cell lymphoma. The patient received systemic chemotherapy and remained free of disease for 16 months after surgery.