The most common cause for an abdominal aortic aneurysm is atherosclerosis. A person with atherosclerosis has narrowing and hardening of the arteries, which carry blood from the heart to the body. The process of atherosclerosis starts in late adolescence and in the early twenties.

Less common causes of an abdominal aortic aneurysm include:

• Abdominal injury
• Bacterial infection:
• Mycotic aneurysm
• Ehlers-Danlos syndrome
• Marfan's syndrome