Mediastinal mass is a rare presentation of tuberculosis in children. The sources of posterior mediastinal mass are usually neurogenic tumors, infections or vascular lesions. Herein, a 12-year-old girl is presented who manifested with a posterior mediastinal mass extending to the right paravertebral space from T3 to T8 with extension to retrocardiac and subcarinal spaces. She suffered from chronic cough, prolonged fever, and weight loss. The results of the tuberculin skin test and biopsy were compatible with tuberculosis. Mediastinal tuberculosis was confirmed histologically and by polymerase chain reaction. The patient was treated with anti-tuberculosis drugs and surgical intervention.