Introduction: This study is aimed at investigating the potential prognostic impact of the preoperatively assessed platelet-to-lymphocyte ratio (PLR) in a European cohort of patients with non-metastatic upper tract urothelial carcinoma (UTUC). Materials and Methods: Clinicopathological data from 180 consecutive non-metastatic UTUC patients, operated between 1990 and 2012 at a single tertiary academic center, were evaluated retrospectively. The preoperative PLR was assessed one day before surgery. Patients were categorized using a PLR cut-off value according to receiver-operating curve analysis. Cancer-specific survival (CSS) and overall survival (OS) were assessed using the Kaplan-Meier method. Additionally, multivariate proportional Cox regression models were applied. Results: In multivariate analyses, age at the date of surgery (<65 vs. ≥65 years, hazard ratio (HR) 1.827, 95% CI 1.051-3.175, p = 0.033), pathologic T-stage (pT1 vs. pT2-4, HR 1.873, 95% CI 1.066-3.292, p = 0.029), and pretreatment PLR (<150.0 vs. ≥150.0, HR 1.782, 95% CI 1.041-3.050, p = 0.035) were independent predictors of OS. Regarding CSS, pathologic T-stage (pT1 vs. pT2-4, HR 2.176, 95% CI 1.062-4.460, p = 0.034) and pretreatment PLR (<150.0 vs. ≥150.0, HR 2.026, 95% CI 1.045-3.930, p = 0.037) were considered independent predictors. Conclusions: In the cohort studied, patients with an elevated (≥150.0) preoperative PLR had a higher cancer-specific mortality and overall mortality after radical surgery for UTUC, compared with those with a low pretreatment PLR.