Objective To investigate the clinical prognostic value of the prognostic nutritional index (PNI) in patients with renal cell carcinoma (RCC) undergoing partial nephrectomy.Methods A retrospective analysis was conducted on the clinical data of RCC patients who underwent partial nephrectomy at our hospital during 2020 and 2024.The optimal cutoff value of PNI was determined based on the maximum Youden index from the receiver operating characteristic (ROC) curve.The clinicopathological characteristics, overall survival (OS), and progression-free survival (PFS) between patients with different PNI levels were compared.Cox regression analysis was used to explore the independent prognostic factors for RCC patients. Results Based on the ROC curve, the optimal cutoff value corresponding to the maximum Youden index was calculated to be 46.675, at which point the sensitivity was 65.3% and the specificity was 62.2%.Of the 815 patients included in the study, 293 (36.0%) patients had a PNI＜46.675.Cox regression analysis confirmed that preoperative PNI, tumor diameter, ISUP classification, and ECOG score were independent risk factors for postoperative OS in patients with RCC who underwent PN (P＜0.05).In addition, preoperative PNI, tumor diameter, ISUP classification and ECOG score were independent risk factors for postoperative PFS (P＜0.05).After covariates in the multivariable Cox regression model were adjusted, patients in the low PNI group demonstrated significantly shorter overall survival (HR=2.392, P＜0.001) and significantly poorer progression-free survival (HR=2.076, P＜0.001) compared to those in the high PNI group.Conclusion Preoperative PNI has significant clinical value in evaluating the prognosis of RCC patients undergoing partial nephrectomy.An elevated preoperative PNI is associated with a better prognosis.