A 68-year-old woman was admitted with symptoms of dry cough and stridor. Computed tomography of the chest revealed a cystic, polypoid lesion protruding inside the trachea, extending to the subcarina. The patient underwent a resection of the cyst, which was found to penetrate the wall of the trachea. Most commonly, bronchogenic cysts appear in the medial one third of the lungs or in the mediastinum. This is a rare case of a mediastinal bronchogenic cyst protruding into the trachea.