BCG (Bacillus Calmette-Guerin) vaccine is a widely used vaccine with the recommendation of World Health Organization to protect children against nniliary tuberculosis (TB) and TB meningitis. Severe side effects related to this vaccine mostly manifest in the presence of underlying immunosuppressive disease. In this report, an infant case with unknown chronic granulomatous disease (CGD) who developed disseminated BCG infection after administration of BCG vaccine, was presented. High fever, left axillary lymphadenopathy and hepatosplenomegaly have developed in a 3-month 28-day female infant, without a known health problem, following BCG vaccination. The acid-fast bacilli (ARB) was isolated from the material of excised lymph node cultivated in Lowenstein-Jensen medium, and the isolate was identified as Mycobacterium bovis. Mycobacterium tuberculosis complex DNA was detected in the axillary lymph node sample by polymerase chain reaction. Anti-tuberculous treatment included 20 mg/kg of rifampicin + 10 mg/kg of isoniazid + 15 mg/kg of ethambutol + 30 mg/kg of streptomycin was started. The patient was then further evaluated for immunodeficiency and on the basis of the results of dihydroamine and LAD (lymphocyte adhesion defect) tests, diagnosed as autosomal recessive CGD. Based on the anamnesis, there was no known immunodeficiency history both in the case during neonatal period and her family members. Interferon-gamma therapy, which is recommended for the patients with CGD living in endemic areas, was initiated. Our patient's fever dropped at the 15th day of anti-tuberculosis treatment, and she was discharged on the 35th day and continued to receive treatment at home. The patient was followed up at outpatient clinic and had no additional complaints; her hepatosplenomegaly was back to normal at the third month. As a result, since BCG vaccine is contraindicated in CGD carriers, newborns with a family history of CGD should be immunologically examined and BCG vaccine should be avoided until the results are obtained. In addition, newborns without a family history, diagnosed as disseminated mycobacterial infection following BCG vaccination, should be evaluated for an underlying immunodeficiency condition.