Aneurysms of the iliac vein are rare. They can occur in association with arteriovenous fistulae located elsewhere. Here, we present a 30-year-old man who developed a large left external iliac vein aneurysm in association with a chronic traumatic arteriovenous fistula in the left thigh. Less than 25 cases of iliac vein aneurysms have been reported in the last 40 years. The presentation and treatment of this condition has been heterogeneous. We suggest that adequate surgical treatment can be offered in a staged approach: aneurysm resection with reconstruction should be done first, followed by closure of the arteriovenous fistula 6 months later.