Intravesical Bacillus Calmette-Guerin (BCG) instillation is preferred as a treatment method in bladder cancer. BCG-related complications are rare but usually self-limiting. Usually, as a result of contamination or inflammation of the urinary system with BCG; local complications such as cystitis, hematuria, bladder contracture, prostatitis, and epididymoorchitis are seen. Severe systemic complications such as fever, acute respiratory failure, hemolytic uremic syndrome, disseminated intravascular coagulation, granulomatous hepatitis, arthritis or arthralgia, rash, skin abscesses, cytopenia, and sepsis are rare. Herein, in this case report, we aimed to present a case of muscle abscess developed after intravesical BCG application to increase clinical awareness.