An increasing number of cases with fenestration that is frequently associated with aneurysms have been reported, largely in the vertebral and basilar arteries and less commonly in the middle and anterior cerebral arteries by angiography as well as by autopsy. However, the anomaly of the internal carotid artery associated with bilateral arterial dissections is exceedingly rare. This represents the first reported case of fenestration of the internal carotid artery associated with arterial dissections. The embryological basis and clinical significance of this anomalous condition are discussed and treatment for arterial dissection is presented.