Acute kidney injury (AKI) is a critical postoperative complication in non-cardiac surgery patients, significantly impacting patient outcomes. The neutrophil percentage-to-albumin ratio (NPAR) is a promising inflammatory biomarker for predicting AKI. However, it is still unclear whether NPAR could be used as a predictor of postoperative AKI in Non-Cardiac Surgical Patients. Univariate and multivariable logistic regression analyses were conducted to assess the predictive value of NPAR for postoperative AKI, controlling for potential confounders. A total of 3041 patients were considered for the analysis after excluding those with preoperative infections and chronic kidney disease. The area under the receiver operating characteristic (ROC) curve for NPAR was 0.723, indicating moderate predictive capability for postoperative AKI. The optimal threshold for NPAR was 5.310, with a specificity of 0.640 and a sensitivity of 0.729. Multivariable regression analysis revealed that NPAR was significantly associated with postoperative AKI risk (adjusted odds ratio 1.093, 95% CI 1.072-1.116, P < 0.001), independent of other clinical factors. Preoperative NPAR is a significant predictor of postoperative AKI in non-cardiac surgical patients under general anesthesia and could be a valuable biomarker for identifying non-cardiac surgical patients at high-risk of AKI.