A 62-year-old female presented with rapid aggravation of long-standing facial spasm occurring within a few months. Neuroimaging and angiography demonstrated compression of the root exit zone (REZ) of the facial nerve by an ipsilateral saccular aneurysm at the left vertebral artery (VA)-posterior inferior cerebellar artery bifurcation, in addition to the elongated VA. Neck clipping of the aneurysm and decompression of the REZ from the elongated VA and clipped aneurysm resulted in complete disappearance of the facial spasm. The aneurysm had very thin walls and was apparently about to rupture. Aggravation of long-standing hemifacial spasm may be a warning sign for rapid growth and rupture of a causative aneurysm.