OBJECTIVE: To assess the oncologic outcomes and the safety profile of a reduced-dose versus full-dose BCG regimen in patients with non-muscle-invasive bladder cancer (NMIBC). MATERIAL AND METHODS: We performed a systematic review according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). The PubMed, Embase, and Web of Science databases were searched in January 2022 for studies that analyzed oncological outcomes and compared between reduced- and full-dose BCG regimens. RESULTS: Seventeen studies including 3757 patients met our inclusion criteria. Patients who received reduced-dose BCG had significantly higher recurrence rates (OR 1.19; 95%CI, 1.03-1.36; p = 0.02). The risks of progression to muscle-invasive BC (OR 1.04; 95%CI, 0.83-1.32; p = 0.71), metastasis (OR 0.82; 95%CI, 0.55-1.22; p = 0.32), death from BC (OR 0.80; 95%CI, 0.57-1.14; p = 0.22), and all-cause death (OR 0.82; 95%CI, 0.53-1.27; p = 0.37) were not statistically different. When restricting the analyses to randomized controlled trials, we found similar results. In subgroup analysis, reduced dose was associated with a higher rate of BC recurrence in studies that used only an induction regimen (OR 1.70; 95%CI, 1.19-2.42; p = 0.004), but not when a maintenance regimen was used (OR 1.07; 95%CI, 0.96-1.29; p = 0.17). Regarding side effects, the reduced-dose BCG regimen was associated with fewer episodes of fever (p = 0.003), and therapy discontinuation (p = 0.03). CONCLUSION: This review found no association between BCG dose and BC progression, metastasis, and mortality. There was an association between reduced dose and BC recurrence, which was no longer significant when a maintenance regimen was used. In times of BCG shortage, reduced-dose regimens could be offered to BC patients.