Bacillus Calmette-Guérin (BCG) is a live attenuated form of Mycobacterium bovis, initially used in medicine as a vaccination agent only. The discovery of its antineoplastic effects in bladder cancer has led to the widespread recognition of BCG intravesical instillation as a therapeutic option. Although sepsis following BCG intravesical instillation is rare, it is nonetheless a dreadful and potentially fatal complication. Therapy usually relies on antituberculous therapy and steroids, alongside with intensive care unit admission. The authors report a case of a 67-year-old male patient who developed septic shock with multiple organ dysfunction after intravesical BCG instillation and review the currently available knowledge concerning the risk factors, diagnosis, management and prevention of BCG sepsis.