Duodenal perforation after a blunt abdominal trauma is a rare emergency situation that can result in life-threatening complications. We report on a woman who had a perforation of the duodenum after a supposed mild blunt abdominal trauma. Unremarkable at the initial presentation, the patient presented with acute abdominal pain and a retroperitoneal abscess five days after the initial trauma. The duodenal repair was performed with a Roux-Y anastomosis. Difficulties in diagnosis are very common, but the early recognition of the rupture is essential. The contrast-enhanced CT scan is the gold standard for diagnosis. Surgical management depends on the severity of the trauma and must be chosen on an individual basis.