Aims Primary bladder non-Hodgkin lymphoma (PBNHL) is very rare, especially as extranodal B-small lymphocytic lymphoma (B-SLL). Also, late isolated renal manifestation of PBNHL is extremely unusual. We report a very rare type of extranodal B-SLL of bladder wall with extremely unusual late isolated renal involvement, clinically manifested by nephrotic syndrome and incipient renal failure. A case reportA 56-year-old woman was presented with a solitary tumor of bladder wall, with history of dysuria and night sweating. A transvaginal needle biopsy of the tumor was performed, and diagnosis of primary extranodal B-SLL was made in the absence of bone marrow, lymph node, or blood involvement. She was treated with chemotherapy until the achievement of complete remission. Nine years later, she developed nephrotic syndrome. The renal biopsy revealed parenchymal lymphoma's involvement associated with glomerular lesion. Immunohistochemical analysis confirmed the same imunophenotype of lymphoma cells like in bladder wall nine years ago. Restaging procedure showed no evidence of disease elsewhere. Conclusion To our knowledge, it is the first case of association of very rare primary bladder B-SLL with late isolated renal involvement.