Elevated p53 expression is associated with several kidney diseases including diabetic nephropathy (DN). However, the mechanisms are unclear. We report that expression levels of transforming growth factor-β1 (TGF-β), p53, and microRNA-192 (miR-192) are increased in the renal cortex of diabetic mice, and this is associated with enhanced glomerular expansion and fibrosis relative to nondiabetic mice. Targeting miR-192 with locked nucleic acid–modified inhibitors in vivo decreases expression of p53 in the renal cortex of control and streptozotocin-injected diabetic mice. Furthermore, mice with genetic deletion of miR-192 in vivo display attenuated renal cortical TGF-β and p53 expression when made diabetic, and have reduced renal fibrosis, hypertrophy, proteinuria, and albuminuria relative to diabetic wild-type mice. In vitro promoter regulation studies show that TGF-β induces reciprocal activation of miR-192 and p53, via the miR-192 target Zeb2, leading to augmentation of downstream events related to DN. Inverse correlation between miR-192 and Zeb2 was observed in glomeruli of human subjects with early DN, consistent with the mechanism seen in mice. Our results demonstrate for the first time a TGF-β–induced feedback amplification circuit between p53 and miR-192 related to the pathogenesis of DN, and that miR-192–knockout mice are protected from key features of DN.