The existence of primary renal lymphoma (PRL) in the kidney has long been debated due to its extranodal location and lack of lymphatic channels. Primary renal lymphoma is extremely rare, accounting for less than 1%, and is frequently misdiagnosed as renal cell carcinoma (RCC). We present a 50-year-old man presenting with right flank pain in the last week. The computed tomography scan showed a large isodense right renal mass with a small para-aortic lymph node suspected of RCC. The patient underwent right radical nephrectomy and lymphadenectomy with an uneventful postoperative outcome. The histopathology and immunohistochemistry showed diffuse large B-cell lymphoma. Then, the patient received five-cycle chemotherapy and regional radiotherapy. Within five years of follow-up, no symptoms of recurrence. In conclusion, even though PRL is a rare tumor type. An effort should be made to make a preoperative diagnosis because PRL can be treated with systemic chemotherapy instead of other renal tumors requiring nephrectomy.