Unruptured cerebral aneurysms often present with neuro-ophthalmological symptoms but ocular autonomic involvement from an aneurysm of the posterior circulation has not previously been reported. A patient is described with a basilar artery aneurysm presenting with headache and unilateral autonomic symptoms. After angiographic coiling of the aneurysm there was a near complete resolution of these features. The relevant anatomy and proposed mechanism of autonomic involvement of what may be considered--from a pathophysiological perspective as a secondary trigeminal-autonomic cephalgia--is discussed