Empyema necessitatis refers to empyema that extends into the extrapleural space through a defect in the pleural surface. Tuberculous empyema necessitatis is a rare complication of tuberculosis. We experienced a 21-month-old boy with tuberculous empyema necessitatis with osteomyelitis in the right 7th rib. He presented with a mass on the right lateral chest wall, which was soft and nontender, enlarging for one month. He also had mild fever. The plain radiograph of his chest revealed soft tissue swelling and calcified lymph node on the left axilla, and his PPD skin test was positive. CT scan of the chest showed empyema necessitatis at the right lower chest and upper abdominal walls with osteomyelitis of the right 7th rib. He did not have concurrent pulmonary tuberculosis. Surgery was performed for diagnosis and treatment. In histo-pathologic findings, chronic granulomatous inflammation with caseation necrosis was shown and was positive for acid fast bacilli stain. In addition, M. tuberculosis complex was found as etiology by polymerase chain reaction. The patient has been treated with anti-tuberculous medication without any specific complication.