Adjuvant intravesical immunotherapy is recognized as an effective treatment option for various urological cancer types. It plays a significant role in reducing the risk of recurrence, particularly in high-risk non-muscle-invasive bladder cancer cases. This treatment method is commonly utilized to diminish tumor residues following transurethral resection and prevent disease progression. Among the most frequently employed agents are BCG (Bacillus Calmette-Guérin) and interferon. Adjuvant intravesical immunotherapy is typically administered alongside or following other treatment modalities to minimize local and systemic side effects. Due to its low invasiveness and relatively high efficacy, this treatment holds a crucial place in the management of non-muscle-invasive bladder cancer.