Congenitally absent internal carotid artery with intercavernous anastomosis is an exceedingly rare vascular anomaly. We report such a case in a 65-year-old man with chronic symptoms resembling sporadic transient ischemic attacks. While these patients are usually asymptomatic due to compensatory collateralization, they are at increased risk of aneurysm formation, and thus proper identification is important. This report serves as both a case of a very rare anomaly and as a lesson on how to avoid this misdiagnosis by carotid duplex sonography. Additionally, we review the limited number of published cases of congenitally absent internal carotid artery with intercavernous anastomosis.