Retropharyngeal abscess and descending necrotizing mediastinitis is a potentially life-threatening condition that rarely develops following trauma to the oropharynx in children. We describe a case of a 17-month-old girl with a retropharyngeal abscess that extended to the posterior mediastinum, producing an acute descending necrotizing mediastinitis and pyopneumothorax. Culture of blood and pleural pus yielded Streptococcus pyogenes. The patient underwent repeated drainage and debridement, was treated with antibiotics and recovered. This report aims to review the retropharyngeal abscess with descending necrotizing mediastinitis in children and to highlight the fact that minor pharyngeal trauma, although not significant at first, should be observed with suspicion for serious potential complications.