Background: There is a debate about the functional role of regulatory B cells in the lupus nephritis (LN) pathogenesis. Objective: The aim of the present study was to analyze total B lymphocytes and their subtype regulatory B lymphocytes (Breg) % in systemic lupus erythematous (SLE) patients, in addition to assess their association with LN activity. Patients and Methods: The present study included 19 lupus nephritis (LN) patients, 11 SLE patients without lupus nephritis (non-LN). They were matched with 20 healthy individuals as a control group. LN activity was evaluated by Renal SLEDAI (rSLEDAI), nephritis patients were divided into active lupus nephritis (renal SLEDAI≥4) and non-active lupus nephritis patients (renal SLEDAI = 0). Full history taking, clinical examination and baseline laboratory investigations were done for all participants. Total B lymphocytes and their subtypes Breg were measured by flow cytometry. Results: SLE diseased patients have significantly higher total B lymphocytes compared to matched controls; also, SLE diseased patients (LN and non-LN) have significantly lower CD19+ CD24^hi CD38^hi compared to matched controls, regardless of LN activity. Conclusion: The present study supports B cell and Breg role in aetio-pathogenesis of SLE and also contributes to the onset of LN which indicates a dysfunctional regulatory mechanism.