Background <p>To evaluate the impact of dutasteride, a 5-alpha reductase inhibitor, used alongside intravesical Bacillus Calmette-Guérin therapy on recurrence, progression, metastasis, and disease-free survival in non-muscle invasive bladder cancer patients.</p> Methods <p>A retrospective analysis was conducted on 514 male non-muscle invasive bladder cancer patients treated at a tertiary care Urology Clinic from January 1, 2015, to January 1, 2023. All participants received intravesical Bacillus Calmette-Guérin therapy induction therapy weekly for six weeks post-transurethral bladder tumor resection, followed by maintenance therapy. Sociodemographic data were collected, and patients were divided into dutasteride users and non-users. Propensity Score Matching minimized group differences. Survival times were assessed using the Kaplan-Meier method, and Cox regression models were applied for further analysis.</p> Results <p>Of the 514 patients, 257 used dutasteride. Median follow-up time was 67 months (IQR: 48–89 months). Dutasteride users were associated with significantly improved disease-free survival, recurrence-free survival, and progression-free survival (all <i>p</i> &lt; 0.001). Metastasis incidence was significantly lower in dutasteride users (<i>p</i> &lt; 0.001). Incidental bladder cancer detection rates during BPH assessment were similar between groups (28.4% vs. 28.4%).</p> Conclusions <p>Dutasteride use, in conjunction with transurethral bladder tumor resection and Bacillus Calmette-Guérin therapy, is associated with improved survival outcomes and reduced metastasis risk in non-muscle invasive bladder cancer patients, suggesting its potential as an adjuvant therapeutic option.</p> Trial registration <p>Not applicable.</p>