A case of mycotic carotid artery aneurysm due to cervical lymphadenitis in a four-year old child is presented. Sonography and computed tomography (CT) demonstrated an irregular fluid-containing neck mass, similar in appearance to an uncomplicated abscess. Continuity with the carotid artery was suggested on sonography, and CT demonstrated intense contrast enhancement of the liquid portion of the mass. Mycotic carotid artery aneurysm is a rare, but potentially fatal, complication of cervical lymphadenitis that is detectable with noninvasive diagnostic imaging studies.