We report a case of a duodenal duplication cyst complicated by infection. An 8-year-old boy was brought to our hospital with severe abdominal pain and a fever of 39.8 degrees C. He had a 5-year history of occasional abdominal pain with vomiting. On examination, a cystic mass was felt under the liver. We performed percutaneous drainage of the cyst under a suspected diagnosis of a choledochal cyst complicated by acute biliary infection. A contrast study through the drainage tube and surgical exploration revealed a duodenal duplication cyst communicating with the second part of the duodenum. The patient had an uneventful recovery and remains well 5 years after surgery. To the best of our knowledge, this is the first documented case of an infected duodenal duplication cyst successfully treated by resection after percutaneous drainage.