Introductionneutrophil/lymphocyte ratio (NLR), as a biomarker of the systemic inflammatory response, has been studied for diverse tumors. Our study aims to determine whether the NLR can be reliably used as a tool to predict disease course in patients diagnosed with primary non-muscle invasive bladder tumors (NMIBC).Methodsa retrospective study between 2009 to 2014 was conducted on 300 patients newly diagnosed with NMIBC at our institution. The cut-off value of NLR was set at 2.5. Survival curves were compared using the log-rank test. The association between recurrence, progression, and NLR was assessed univariate, and the prognostic significance of high NLR was assessed using multivariate analysis.Resultsone hundred and seventy-five patients had an NLR <2.5 and 125 patients had an NLR ≥ 2.5. The survival rate with recurrence at 5 years was higher in the group with an NLR >2.5 (p<0.001, 35 vs 18 months), similarly, the survival rate with progression at 5 years was higher in the group with an NLR > 2.5 (p=0.001, 36 vs. 27 months). The failure rate of immunotherapy using BCG was higher when the NLR was over 2.5. In a multivariate analysis, the factors associated with recurrence were NLR>2.5 (HR=2.03, 95% CI=1.32-3.11, p=0.001), pathologic stage pT1 (HR=2.42, 95% CI=1.52-3.85, p=0.001), high-grade (HR=1.76, 95% CI=1.52-3.92, p=0.01), concomitant CIS lesions (HR=2.31, 95% CI=1.36-3.92, p=0.001), presence of lymphovascular emboli (HR=5.77, 95% CI=1.77-18.78, p=0.004), and BCG immunotherapy failure (HR=5.29, 95% CI=2.88-9.70, p=0.001). With regard to progression, in a multivariate study, the significant factors were NLR>2.5(HR=2.91, 95% CI=1.17-7.23, p=0.01), BCG immunotherapy failure (HR=5.68, 95% CI=3.16-10.22, p=0.001), and the presence of lymphovascular emboli (HR=5.01, 95% CI=1.50-16.05, p=0.001).Conclusionpreoperative NLR value could predict recurrence, progression, and failure of BCG immunotherapy in NMIBC patients.