The formation of a traumatic arteriovenous fistula (AVF) between the extracranial middle meningeal artery (MMA) and the pterygoid plexus (PP) is very rare, and understanding of this condition is limited. This paper reports the case of an 8-year-old who suffered minor injuries after a high fall four months prior to admission and showed good recovery after one month. However, the child gradually developed exophthalmos of the left eye and conjunctival redness one month prior to admission. Auscultation revealed an intracranial murmur near the left side of the face, in the temporal region. A digital subtraction angiography (DSA) showed rupture of the left extracranial MMA and an AVF between the MMA and the PP. The blood drained toward the cavernous sinus, resulting in retrograde blood flow into the ophthalmic vein and the cortical vein. The diagnosis was an AVF between the MMA and the PP, and a combination of coils and Onyx liquid embolic agent was employed to perform AVF embolization. Follow-up six months later indicated no recurrence of the AVF, and the patient showed good recovery with a normal-appearing left eye. The AVF in this case drained toward the cavernous sinus, and symptoms of increased intracranial venous system pressure were apparent, similar to those produced by fistulas between the internal carotid artery and the cavernous sinus. This condition is very rare, and the use of coils in combination with Onyx for AVF embolization is novel, warranting the reporting of the current case.