Bacillus Calmette-Guérin (BCG) is a live, attenuated strain of Mycobacterium bovis that is used to treat superficial bladder cancer. Although its use is typically associated with only mild, localized side effects, rare systemic complications can occur. Disseminated mycobacterium infections after BCG therapy have been reported in over 30 cases; however, central nervous system (CNS) infections do not commonly occur. We report a 74-year-old male who developed a M. bovis cerebellar abscess after receiving intravesical BCG infusion for bladder cancer for less than 1 year. This patient was successfully treated with antituberculosis therapy and corticosteroids. This patient case demonstrates that early-onset M bovis CNS infections can occur after BCG therapy. Patients presenting with altered mental status while on BCG therapy should be evaluated for disseminated infections.