Tuberous sclerosis complex (TSC) is an autosomal dominant disorder with multisystem clinical manifestations. Dysplastic proliferations of small blood vessels including hemangiomas are common; however, anomalies of medium- and large-size vessels are rare. The only extracranial carotid artery aneurysm in a patient with TSC was reported in 1998. Since then, 19 cases have documented intracranial aneurysms in patients with TSC. The case of two of three identical triplet sisters with TSC who were treated for extracranial carotid artery aneurysms is presented. To the authors' knowledge, this is the first reported case of monozygotic siblings who both manifested this rare expression of TSC.