AbstractIron plays an important role in hemodynamics and the immunity, independent of anemia. Since dynamic changes occur in iron storage after kidney transplantation (KT), we investigated the association between iron status and kidney outcomes in KT patients. We analyzed data from the KoreaN cohort study for Outcome in patients With KT (KNOW-KT). The iron status was classified into three groups based on ferritin or transferrin saturation (TSAT) levels one year after KT, with reference ranges of 20‒35% and 100‒300 ng/mL for TSAT and ferritin, respectively. The primary outcome was the composite outcome, which consisted of death, graft failure, and an estimated glomerular filtration rate decline ≥ 50%. In total, 895 patients were included in the final analysis. During a median follow-up of 5.8 years, the primary outcome occurred in 94 patients (19.8/1000 person-years). TSAT levels decreased one year after KT and thereafter gradually increased, whereas ferritin levels were maintained at decreased levels. The adjusted hazard ratios (95% confidence intervals) for the composite outcome were 1.67 (1.00–2.77) and 1.20 (0.60–2.40) in the TSAT > 35% and ferritin > 300 ng/mL groups, respectively. High iron status with high TSAT levels increases the risk of graft failure or kidney functional deterioration after KT.