Immunotherapy with BCG for non-invasive or superficial bladder cancer is the standard adjuvant t reatment following transurethral resection. Despite its effectiveness and safety, approximately 1 to 5% of patients experience local or disseminated (BCGitis) infectious adverse effects. We present the case of an 80-year-old male patient with a history of bladder cancer undergoing intravesical immunotherapy during the induction phase, hospitalized due to a month long historyof generalized weakness, acute kidney injury, and a positive urine culture for Escherichia coli ESBL (+). Prior to a new dose of immunotherapy, treatment with imipenem was initiated. Abdomen and pelvic computed tomography (CT) scan revealed a left periprostatic inflammatory collection involving the ipsilateral ureter with proximal hydronephrosis, a finding justified by the patient's medical history. After completing treatment, he experienced a fever peak and an increase in inflammatory parameters. A new CT scan showed growth of the collection. Abscess puncture was performed with an extended study, obtaining positive acid-fast bacillus microscopy and amplification of specific nucleic acids, confirming the diagnosis of urogenital abscess caused by BCG. Therapy with rifampicin, isoniazid and ethambutol was initiated, achieving clinical improvement.