The bacillus Calmette-Guérin (BCG) vaccine is a safe live vaccine mainly administered to infants to prevent tuberculosis; complications rarely occur after administration of the BCG vaccine. Herein, we report the case of an infant who developed a rare complication of a tuberculous abscess in the chest wall and osteomyelitis in the ribs after administration of the BCG vaccine at 1 month of age. An 11-month-old male infant was admitted to the hospital due to a palpable mass in the right anterolateral chest area detected about a month before hospitalization, with no tenderness, erythema, or lymphadenopathy. After thoracic computed tomography and ultrasonography, the cause of the abscess was suspected to be mycobacterial infection and the abscess was removed under general anesthesia. Chronic granulomatous inflammation with caseous necrosis was detected through a biopsy, and polymerase chain reaction was performed and <i>Mycobacterium tuberculosis</i> complex was detected. However, staining for acid-fast bacteria and microbiological cultures were negative. Based on these results, the patient was diagnosed with a tuberculous abscess and osteomyelitis in the chest wall owing to administration of the BCG vaccine. After being medicated with isoniazid and rifampicin for 6 months, the patient was successfully treated.