Secondary aortoduodenal fistula (sADF) is a rare but very serious cause of gastrointestinal hemorrhage, difficult to diagnose, and a potentially fatal disease. We report 3 patients with aortic prostheses who were hospitalized for gastrointestinal bleeding due to sADF, and discuss their clinical diagnosis, treatment, and final results. All of them underwent surgical interventions and were successfully rescued once, but two of them succumbed due to postoperative infectious complications. In cases of gastrointestinal hemorrhage after aortic prostheses, clinical suspicion of sADF and an early diagnostic abdominal CT scan with anticipation of its high sensitivity and specificity for sADF are crucial. Early surgical intervention with removal of prosthetic aortic graft should be considered to control systemic infections and survival.