Iatrogenic esophageal perforation is very rare in pediatric patients. Preterm infants or low birth weight babies are more susceptible to esophageal perforation due to performing frequent tracheal intubation and/or gastric tube installation. When perforation occurs, it may present as pneumothorax and pulmonary interstitial emphysema. However, isolated pneumomediastinum without pneumothorax is a rare finding. Furthermore, the mediastinitis after esophageal perforation is rare complication, but it can be a critical complication. Therefore, making an immediate and precise diagnosis as well as instituting proper treatment of esophageal perforation and mediastinitis are important. To the best of our knowledge, few reports have described mediastinitis after pneumomediastinum that was secondary to esophageal perforation. We describe here the radiologic findings of a rare case of mediastinitis after pneumomediastinum in a preterm infant with esophageal perforation.