The aim of this study was to investigate the association of urinary transferrin with allograft function and renal function decline in kidney transplant recipients (KTRs). Thirty KTRs whose eGFR were less than 60 mL/min/1.73m2 (chronic allograft injury group) and 20 KTRs with normal allograft function group (control group) were included in this study. Though urinary proteomic analysis with LC-MS/MS, several urinary proteins including transferrin were identified and then validated by ELISA. Rapid renal function decline was defined as eGFR decline of >3 mL/min/1.73m2/year or initiation of dialysis, and 19 (38%) were included in rapid renal function decline group. Among protein profiles identified by proteomics, urinary transferrin levels were different between chronic allograft injury group and control group (63219 ± 42817 vs. 11192 ± 10535, P<0.001). Urinary transferrin/creatinine ratio measured by ELISA were also higher in chronic allograft injury group than control group (9.2 ± 8.0 vs. 4.0 ± 3.3, P=0.003), and had high association with chronic allograft injury group (AUC 0.753, 95% confidence interval [CI] 0.615-0.891, P<0.001) in ROC curve analysis. Additionally, urinary transferrin/creatinine ratio were higher in patients with rapid renal function decline than in those with stable renal function (11.6 ± 8.8 vs. 4.3 ± 3.6, P=0.002). Univariate logistic regression analysis revealed that urinary transferrin/creatinine ratio were significantly associated with rapid renal function decline (odds ratio [OR] 1.30, 95% CI 1.12-1.57; P=0.002). Multiple logistic regression showed urinary transferrin/creatinine ratio remained a significant risk factor for rapid renal function decline (OR 1.30, 95% CI 1.07-1.74; P=0.033). ROC curve analysis also revealed the AUC of 0.832 (95% CI 0.722-0.942, P<0.001) for urinary transferrin/creatinine ratio in predicting rapid renal function decline. Urinary transferrin/creatinine ratio might be a potential biomarker for detection of chronic allograft injury and could be used as predictor for rapid renal function decline in KTRs.