Klotho-derived peptide 1 (KP1) (56-87), a peptide originating from the human Klotho protein, disrupts TGF-β signaling by binding to TGF-β receptor types 1 and 2 (TGFBR1 and TGFBR2; Kds = 1.41 and 14.6 µM, respectively). Preincubation with KP1 at a concentration of 10 µg/ml hinders the TGF-β-induced escalation of fibronectin and α-smooth muscle actin (α-SMA) levels in NRK-49F rat fibroblasts. Furthermore, in vivo studies reveal that KP1, administered at 1 mg/kg per day, preferentially accumulates in damaged kidneys, leading to significant reductions in serum creatinine and blood urea nitrogen levels, indicators of improved kidney function. Additionally, it decreases kidney fibrosis in mouse models of unilateral ureteral obstruction (UUO) and unilateral ischemia-reperfusion injury-induced renal fibrosis.