A 71-year-old female on hemodialysis was referred to our hospital for a left renal mass which was incidentally found during a medical check-up. Abdominal computed tomography with intravenous contrast enhancement showed an iso-dense enhanced mass. Under the diagnosis of renal cell carcinoma, retroperitoneoscopic radical nephrectomy was performed. Histopathological examination revealed follicular lymphoma. This was the 20th case of primary renal lymphoma in Japan.