Objectives Atherosclerosis is the most common etiologic factor for extracranial carotid artery aneurysm in adults, while in childhood, connective tissue diseases, peritonsillar abscess and infections are the most common. Congenital carotid artery aneurysms are rarely reported in the literature. Methods We present a 10-year-old girl with congenital extracranial left internal carotid artery aneurysm and the treatment management. Results Computed tomography angiography at six months showed that internal carotid artery segments were normal. There was no obstruction or aneurysm recurrence. Conclusions Although extracranial carotid artery aneurysms are rare, they can cause complications such as rupture and thromboembolism with high mortality and morbidity. Therefore, the treatment of extracranial carotid artery aneurysms is recommended.