Intravesical Bacillus Calmette-Guérin (BCG) treatment for superficial bladder cancer is interrupted in approximatively 8% of cases as a result of complications. The objective is to report the severe related complications of Bacillus Calmette-Guérin (BCG) following an intravesical instillation for bladder tumor encountered at our institution for the past 5 years. Medical records of a tertiary teaching hospital, located in Beirut, Lebanon, were retrospectively analyzed from June 2014 to June 2019 searching for severe related complications of BCG. A comprehensive review of articles on this subject was conducted. The incidence of severe systemic adverse events related to BCG instillation was 1.5% (5 out of 332 patients). A total of five patients were found to have a severe BCG related complication, with fever, chills, and irritative urinary signs being the most frequent symptoms. All patients received antituberculosis therapy (Isoniazid, Rifampin and Ethambutol). Two were put on add-on corticosteroids. Three patients had a computed tomography scan image in favor of an infection. Two patients had a favorable outcome, three patients died. BCG severe adverse events were mostly seen in patients with a traumatic instillation. Treatment used at our institution was similar to most cases reported in the literature. A standardized diagnostic and treatment approach should be implemented to help physicians tackle these life-threatening complications. © 2020 The Authors.