BACKGROUND Diabetic nephropathy (DN), which is one of the primary causes of end-stage renal disease (ESRD), is increasingly diagnosed in patients due to the continuous increase in the prevalence of diabetic mellitus (DM). Astragali Radix, a traditional Chinese herb, is widely administrated to ameliorate the symptoms of diabetes and diabetic nephropathy, but its mechanism is still not yet fully defined. Calycosin (C₁₆H₁₂O₅) is the major active component of Astragali Radix. In this study, we analyzed the role of calycosin in diabetic nephropathy and explored its underlying mechanism. MATERIAL AND METHODS Cell activation, inflammatory cytokines expression and secretion, and protein levels were analyzed in cultured mouse tubular epithelial cells (mTEC). db/db mice were intraperitoneally injected with 10 mg/(kg·d) calycosin or control saline for 4 weeks, followed by analysis of structure injury, inflammation, and NF-κB signaling activity. RESULTS Our results indicated that TNF-α and IL-1β were significantly induced by advanced glycation end-products (AGEs), but calycosin remarkably reduced the expression of TNF-α and IL-1β in the cultured mouse tubular epithelial cells (mTEC). Calycosin effectively alleviated kidney injury in diabetic kidneys of db/db mice during the progression of diabetic renal injury, indicated by the reduction of histological injury and immunohistochemical of inflammatory cytokines. Mechanistically, we identified calycosin inhibited diabetes-induced inflammation in kidneys by suppressing the phosphorylation of IKBa and NF-κB p65 in vitro and in vivo. CONCLUSIONS Calycosin significantly ameliorated diabetes-induced renal inflammation in diabetic renal injury by inhibition of the NF-κB-dependent signaling pathway in vivo and in vitro.