The Naples prognostic score (NPS) is an effective and objective tool to assess the immune-nutritional status of patients with malignant tumors. The aim of this study was to investigate the clinical significance of preoperative NPS on short- and long-term outcomes after pancreatoduodenectomy (PD) for ampullary carcinoma.We retrospectively analyzed 404 consecutive patients with ampullary carcinoma who underwent PD between January 2012 and June 2018. Preoperative NPS was calculated from serum albumin and total cholesterol concentrations, and the neutrophil-lymphocyte ratio and lymphocyte-monocyte ratio (LMR). Patients were then divided into three groups according to their NPS. Clinicopathological variables, postoperative outcomes, and survival data were compared between the three groups. Univariate and multivariate Cox analysis of overall survival (OS) and recurrence-free survival (RFS) were also conducted, and time-dependent receiver operating characteristic (ROC) curves were created to evaluate the discriminatory ability of the prognostic scoring systems.Patients with higher NPS had worse prognosis, and significant OS difference (group 0 vs. 1, P=0.02; group 1 vs. 2, P<0.001; group 0 vs. 2, P<0.001) and RFS difference (group 0 vs. 1, P=0.088; group 1 vs. 2, P<0.001; group 0 vs. 2, P<0.001). Multivariate analysis revealed that NPS was an independent significant predictor of OS (grade 2 vs. grade 1 or 0, hazard ratio: 3.067; P<0.001) and RFS (grade 2 vs. grade 1 or 0, hazard ratio: 2.732; P<0.001). The time-dependent receiver operating curve analysis showed that NPS had better prognostic performance for OS and RFS than other prognostic models. Additionally, significant differences in the incidence of postoperative morbidity were observed between the three groups, and the NPS was an independent risk factor of overall postoperative complications (grade 2 vs. grade 1 or 0, odds ratio: 1.692; P=0.02).The NPS was an independent predictor of overall- and RFS in patients undergoing PD for ampullary carcinoma, and was independently associated with the incidence of postoperative complications.2021 Hepatobiliary Surgery and Nutrition. All rights reserved.