Intravesical Bacillus Calmette-Guérin (BCG) immunotherapy in bladder cancer patients with asymptomatic bacteriuria (ABU) remains a matter of debate. The aim of this systematic review was to present available evidence on the safety and efficacy of BCG immunotherapy in patients with ABU. A literature search within the Medline and the Embase databases was conducted with the following search terms: adverse events, bacteriuria, BCG, bladder cancer, cystitis, infection, pyuria, side effects and urinary tract infection (UTI). Sixteen relevant original articles were identified, including 6 articles directly presenting the safety or efficacy of BCG therapy in patients with ABU. None of them was a randomized controlled trial. Intravesical BCG instillations in patients with ABU were not associated with the increased risk of symptomatic UTI and did not affect negatively the recurrence- or progression-free survival. Routine urine analysis before BCG instillation created increased cost and potentially unnecessary delays in BCG therapy. ABU does not affect negatively the safety and efficacy of intravesical BCG immunotherapy. There is no evidence to support routine screening and treatment of ABU in patients scheduled for intravesical BCG instillations due to bladder cancer. However, this issue was not addressed adequately and needs further research.