We report on a case of a giant aneurysm of the internal carotid artery in a 11-year old boy presenting with gradual unilateral visual loss, combined with slight headache and retro-orbital pain. Endovascular balloon occlusion of the internal carotid artery combined with monitoring of somatosensory evoked potentials was performed. Follow-up MR imaging six months after balloon occlusion revealed complete thrombosis and considerable retraction of the aneurysm. However, visual loss persisted, since therapy was initiated too late and optic nerve atrophy had already occurred. It is important to emphasize that visual disturbance should be considered as an emergency, and, although rare, aneurysms do occur in the pediatric population.