Background: Exosomes can be secreted from bone marrow mesenchymal stem cells (BMSCs) to extracellular space and exert anti-fibrotic effects, but the underlying mechanisms remain to be elucidated. Methods: 5/6 subtotal nephrotomy (SNx) rat models and TGF-\beta1-induced human renal proximal tubular epithelial cells (HRPTEpiCs) were established to simulate renal fibrosis. Renal function and fibrosis were assessed by Hematoxylin and Eeosin (HE) staining, Masson staining, immunohistochemistry, and western blot. The expression of Smad 7/Smurf 2 was detected in rats and HRPTEpiCs by western blot, and a further potential mechanism was explored using si-Smurf 2. Results: BMSC-Exo improved renal function, reduced the fibrotic region, down-regulated the expression of fibronectin, Collagen-I, \alpha-SMA, and up-regulated E-cadherin in SNx models. In vitro study demonstrated that knocking down the expression of Smurf 2 significantly increased the expression of Smad 7, which could be enhanced by BMSC-Exo. BMSC-Exo could alleviate the fibrosis induced by TGF-\beta1 in tubular epithelial cells and enhanced the protective effect of si-Smurf 2 on renal fibrosis. Conclusions: BMSC-Exo inhibited renal fibrosis both in vivo and in vitro, partially, by regulating the Smurf 2/Smad 7 axis. BMSC-Exo enhanced the protective effect of si-Smurf 2 on fibrosis induced by transforming growth factor-\beta1 (TGF-\beta1).