This study aims to determine the prognostic value of preoperative Naples prognostic score (NPS) on survival outcomes in upper tract urothelial carcinoma (UTUC) patients after radical nephroureterectomy (RNU). We conducted a retrospective study about UTUC patients at West China Hospital from January 2015 to June 2019. The X-Tile program was used to identify the optimal cutoff value of NPS. Overall survival (OS), cancer-specific survival (CSS) and progression-free survival (PFS) were the endpoints of interest. Kaplan-Meier curves were used to estimate survival and Cox proportional hazard model was used for risk assessment. A total of 237 UTUC patients after RNU were identified and the threshold of NPS was determined to be 2. Preoperative high-NPS was associated with inferior OS (p = 0.004), CSS (p = 0.002) and PFS (p = 0.008), especially in locally advanced UTUC patients. Preoperative NPS was an independent predictor for OS (HR: 1.78; 95% CI: 1.08, 2.93), CSS (HR: 1.87; 95% CI: 1.11, 3.14) and PFS (HR: 1.60; 95% CI: 1.02, 2.50). The addition of NPS into the predictive model consisting of predictors from multivariate Cox regression resulted in better prediction performance. Preoperative NPS was a novel and reliable predictor for survival in UTUC patients after RNU, and should be further explored.