An aortoesophageal fistula is one of the very few causes of upper gastrointestinal bleeding but can be fatal if the diagnosis is delayed. This usually occurs secondary to esophageal or aortic surgery. A primary aortoesophageal fistula is rare and less likely to be suspected. Here, we present a case of a primary aortoesophageal fistula that presented as massive upper gastrointestinal bleeding. An 81-year-old man with a history of aortic aneurysm had syncope and bright color hematemesis. The aortoesophageal fistula was not diagnosed early enough and the patient died. Therefore, emergency physicians should consider aortoesophageal fistula as a potential cause when encountering upper gastrointestinal bleeding.