A 77-year-old woman who complained of dysphagia was found to have an aneurysm in the descending aorta. Magnetic resonance imaging (MRI) demonstrated the state of thrombi, a thin and irregular soft tissue signal between the aneurysm and the esophagus, which suggested an esophago-aneurysmal fistula revealed by the operation. MRI was effective in the evaluation of the status of aneurysm.