This paper reports that decompression of the facial nerve by transarterial Onyx embolization may relieve hemifacial spasm (HFS) caused by dilated veins due to a right petrosal dural arteriovenous fistula (DAVF). A 56-year-old man suffered severe chronic right HFS associated with a dilated right petrosal vein lying in the vicinity of the facial nerve. The right petrosal DAVF was reached through the middle meningeal artery using a transfemoral arterial approach and was occluded with Onyx 18 (M.T.I.- ev3, Irvine, CA, USA). There was complete remission of HFS without recurrence after two months of follow-up. This case supports vascular compression in the pathogenesis of HFS and suggests that facial nerve injury caused by a DAVF could be treated with transarterial Onyx embolization.