CD4(+)CD25(+) cells are critical regulators in almost all of the animal models of human organ-specific autoimmune diseases, transplant rejection and allergic diseases. We aimed to explore the role of CD4(+)CD25(+) cells in the pathogenesis of multiple myeloma (MM) related renal impairment (RI). Thirty patients with MM related RI and 30 healthy volunteers were studied. The number of CD4(+)CD25(+) cells was examined by flow cytometry. Clinical and laboratory data were collected from each subject. Glomerular injury was assessed by histopathology. Serum IL-2, IL-4 and IL-6 were analyzed by ELISA. CD4(+)CD25(+) cells significantly decreased in MM related RI patients compared to the controls (P<0.05). CD4(+)CD25(+) cell number was negatively associated with blood urea nitrogen (BUN), supernatant IL-4, serum IL-6, monoclonal immunoglobulin and β2-microglobulin, as well as bone marrow plasma cell percentage and proteinuria; whereas positively associated with estimated glomerular filtration rate (eGFR) (all P < 0.05). CD4(+)CD25(+) cells gradually decreased as the Clinic Stage increased. The number of CD4(+)CD25(+) cells reduced in MM related RI patients, and was correlated with disease severity. CD4(+)CD25(+) cells may play an important role in the pathogenesis of MM related RI.