Bacille Calmette-Guerin intravesical treatment is the most effective treatment for reducing the recurrence of non-muscle-invasive urothelial carcinomas. This treatment can sometimes have side effects and serious complications. Granulomatous prostatitis is a common histological finding but it rarely has a clinical presentation. We report a case of a 75-year-old, type 2 diabetic, male patient who was diagnosed with urothelial in situ carcinoma, for which he began treatment with Bacille Calmette-Guerin instillations. Five years later the patient presented nocturia, pollakiuria, severe urgency, and intense and recurrent perineal pain associated with marked elevation of prostatic specific antigen. A prostatic biopsy was performed that showed a moderate to severe granulomatous prostatitis related to bacille Calmette-Guerin. The patient received full antituberculosis combination drugs with a favorable clinical response.