Tracheal diverticula are relatively rare disease characterized by single or multiple evaginations of the tracheal wall. The tracheal diverticulum may act as a reservoir for secretions, leading to recurrent respiratory tract infections associated with chronic cough and dyspnea. A 31-year-old man had complained of a chronic productive cough for several months. Methacholine bronchial provocation test was positive. Three-dimensional computed tomography showed an air-containing cystic structure extending right posterolateral aspect of the trachea. Fiberoptic bronchoscopy demonstrated ostium arising from the right posterolateral wall at mid-third of trachea. These findings made asthma and tracheal diverticulum the diagnosis. Medical treatment was performed and symptoms were relieved.