Renal tubulointerstitial inflammation has an important role in fibrosis, which is the main pathogenetic alteration associated with chronic kidney disease (CKD). The left?right determination factor?1 (Lefty?1) gene pleiotropically and biologically regulates transforming growth factor, mitogen?activated protein kinase and other signaling pathways, and is considered to have a potential anti?inflammatory function. However, its role in renal tubulointerstitial inflammation, which is often a long?term consequence of renal fibrosis, is currently unknown. In the present study, the effects of adenovirus?mediated overexpression of Lefty?1 (Ad?Lefty?1?flag) on renal tubulointerstitial inflammation were determined using a mouse model of unilateral ureteral obstruction (UUO) and a rat renal tubular duct epithelial cell line?(NRK?52E), which was treated with lipopolysaccharide?(LPS). In?vivo results indicated that the inflammatory response was increased in UUO mice, as evidenced by the increase in inflammatory cytokines and chemokines. Conversely, Lefty?1 significantly reversed the effects of UUO. Furthermore, the results of the in?vitro study demonstrated that Lefty?1 significantly inhibited LPS?induced inflammatory marker expression in cultured NRK?52E cells via the nuclear factor (NF)?κB signaling pathway. These results suggested that Lefty?1 may ameliorate renal tubulointerstitial inflammation by suppressing NF?κB signaling. In conclusion, the findings of the present study indicated that Lefty?1 may be considered a potential novel therapeutic agent for inhibiting renal tubulointerstitial inflammation or even reversing the CKD process.