A paratracheal cyst is an air-filled cyst lined by a ciliated epithelium, commonly referred to as a tracheal diverticulum. The most common location of paratracheal cysts is the right side of posterolateral tracheal wall. It occurs in 0.3% to 8.1% of the total population. Most paratracheal cysts are asymptomatic and discovered incidentally on routine radiologic examination. Rarely, however, symptoms such as cough or fever are encountered and chronic infection of the paratracheal cyst usually present itself like a tucoberculosis or a tumor. There are few case reports of deep neck infection caused by a paratracheal cyst. We report a case of retropharyngeal abscess resulting from an infected paratracheal cyst.