In patients with chronic kidney disease (CKD) and a mouse model of unilateral ureteral obstruction (UUO), progressive renal fibrosis was associated with the overactive Smad3 signaling and the development of ferroptosis identified by decreased GPX4 while increasing two ferroptosis biomarkers including the Transferrin receptor 1 (TFR1) and 4-Hydroxynonenal (4-HNE). Here, SMAD3 is linked to renal fibrosis.