BACKGROUND Gastrointestinal injury following blunt abdominal trauma is uncommon; a combined stomach and duodenal perforating injury is even more rare. Because these two organs are located in different spaces in the abdomen, such injuries are difficult to identify. METHODS A young woman involved in a motor vehicle crash presented to our emergency department with concerns of severe peritonitis. Contrast-enhanced computed tomography of the abdomen revealed pneumoperitoneum and retroperitoneal hematoma in zone 1. An emergency laparotomy was performed, revealing a stomach-perforating injury, which was resolved with primary repair. No obvious injury was observed on retroperitoneal exploration. However, peritonitis presented again on the second postoperative day, and a second laparotomy was performed, revealing a duodenum-perforating injury in its third portion. We performed primary repair with multi-tube-ostomy. The patient recovered well without permanent tube placement or internal bypass. CONCLUSIONS Assessing associated injuries in blunt abdominal trauma is crucial because they may be fatal if timely intervention is not undertaken. These types of complicated injuries require a feasible surgical strategy formulated by experienced surgeons, which gives the patient a better chance of survival.