Paradoxical response refers to the enlargement of old lesions or unexpected appearance of new lesions after initial improvement following treatment with antitubercular agents. Various types of paradoxical responses have been reported in the world, but they are rarely reported in Korean children. We report the case of a 17-year-old boy who was diagnosed with tuberculous pleurisy and was treated appropriately. Although the tuberculous pleurisy initially responded to medication with resolution of the pleural fluid, a new pulmonary lesion subsequently developed 3 weeks after the initiation of treatment that eventually cleared with continuation of the original drug regimen.