BACKGROUND: The C-reactive protein (CRP)/albumin ratio is a useful index used to represent patient inflammation and nutritional status. Elderly patients are at the highest risk for acute kidney injury (AKI). We clarified the impact of the preoperative CRP/albumin ratio on AKI and evaluated the impact of postoperative AKI on end-stage renal disease (ESRD) among elderly cystectomy patients. METHODS: We included elderly patients ≥ 65 years of age who underwent radical cystectomy. Multivariate logistic regression analysis and receiver operating characteristic curve analysis were performed to identify risk factors for AKI. Propensity score-matched analysis and conditional logistic regression analysis were performed to elucidate the impact of the CRP/albumin ratio on AKI. The incidence of ESRD was compared between the non-AKI and AKI groups at 12 months after radical cystectomy. RESULTS: AKI occurred in 110 patients (32.2%). The CRP/albumin ratio and 6% hydroxyethyl starch amount were risk factors for postoperative AKI. The optimal cut-off value for the CRP/albumin ratio predicting AKI was 0.1. After propensity score matching, the AKI incidence in the CRP/albumin ratio ≥ 0.1 group was higher than that in the CRP/albumin ratio < 0.1 group (46.7% vs. 20.6%, < 0.001), and a CRP/albumin ratio ≥ 0.1 was associated with a higher AKI incidence (odds ratio = 4.111, < 0.001). The ESRD incidence was higher in the AKI group than in the non-AKI group (7.3% vs. 1.2%, = 0.017). CONCLUSION: A CRP/albumin ratio ≥ 0.1 was associated with an increased incidence of AKI, which was associated with higher ESRD incidence among elderly cystectomy patients.