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BACKGROUND The purpose of this study was to investigate whether adding single immediate postoperative intravesical instillation of doxorubicin (SID) to transurethral resection of bladder tumor (TURBT) significantly reduced the risk of recurrence in patients with non-muscle-invasive bladder cancer (NMIBC). MATERIALS AND METHODS We retrospectively analyzed the records of 720 patients diagnosed with primary NMIBC between 2002 through 2018 at the Kameda Medical Center. The primary outcome measure was time to recurrence. Time to progression was also compared. The cohort of SID and the cohort of TURBT alone were matched one-to-one by propensity scores. Matching was done by patient age, gender, and factors of the European Organization of Research and Treatment of Cancer recurrence risk table. The associations of adding SID and clinical outcomes were assessed with uni- and multivariate competing-risk regression models. RESULTS After matching, a total of 364 patients, including 182 receiving SID and 182 receiving TURBT alone, were analyzed. No statistically significant differences existed among the measured baseline characteristics in propensity score-matched cohorts. In the multivariate analysis, there was a significantly longer time to recurrence in patients receiving SID (subdistribution hazard ratio, 0.68; 95% confidence interval, 0.49-0.95; P = .024) in propensity score-matched cohorts. There was no significant difference in time to progression (subdistribution hazard ratio, 0.61; 95% confidence interval, 0.11-3.49; P = .58) in univariate analysis. CONCLUSIONS Our results demonstrated that SID significantly reduced the recurrence risk of primary NMIBC. Doxorubicin could be an inexpensive alternative to other evidenced-based chemotherapeutic agents for single immediate intravesical chemotherapy.