We report the case of a giant fusiform aneurysm of the petrous internal carotid artery in a 15-year-old patient who had presented with headache, hearing loss and Horner's syndrome. Definitive radiological diagnosis was made by non-invasive imaging techniques, including magnetic resonance angiography (MRA). The aneurysm was obliterated by endovascular balloon occlusion following successful tolerance of test occlusion of the internal carotid artery.