BCG (bacille Calmette-Guérin) vaccination is carried out worldwide to prevent tuberculosis. It is considered to be very effective and has an excellent safety profile, but complications do occur. These may range from erythema and abscess at the site of inoculation to extensive disseminated disease including regional and distant lymphadenopathy, lymphadenitis, musculoskeletal lesions and non-fatal and fatal disseminated infections, depending upon the immune status of the patient. Osteomyelitis is a rare but serious complication that may have a fatal outcome. We report a case of severe tuberculous osteomyelitis secondary to BCG vaccination in a child with possible severe combined immune deficiency.