Regulatory T (Treg) cells play an important role in the maintenance of immune tolerance to self and in the pathogenesis of autoimmune disease. Transforming growth factor-beta 1(TGF-β1) is a regulatory cytokine with pleiotropic properties in immune responses. This study was to investigate the role of Treg cells and TGF-β1 in the pathogenesis of patients with lupus nephritis (LN). A total of 42 new-onset systemic lupus erythematosus patients and 22 healthy controls were enrolled. The proportion of Treg cells in peripheral blood mononuclear cells (PBMCs) was evaluated by flow cytometric analysis. The serum and urinary TGF-β1 levels were measured by enzyme-linked immunosorbent assay (ELISA). The results demonstrated a significant decrease in the frequency of CD4(+)CD25(high) and CD4(+)CD25(+)FoxP3(+) T cells in LN patients. The concentration of serum TGF-β1 was found decreased in SLE patients, while urinary TGF-β1 levels were significantly higher in LN patients. Based on our results, decreased Treg cells were accompanied with lower serum TGF-β1 levels and higher urinary TGF-β1 levels in LN patients. TGF-ß1 levels in serum may play a key role in the pathogenesis of renal impairment while the significantly increased urinary TGF-β1 levels may be used as a biological marker in prediction of lupus nephritis.