Posterior communicating artery (PCoA) aneurysm-cavernous sinus fistulae are an extremely rare complication of head injury . The treatment of PCoA aneurysm-cavernous sinus fistulae has not been well described. A 27-year-old man was admitted with a retroocular bruit and blurred vision of the left eye seven months after a severe head injury. We report the angiographic appearance of a posterior communicating artery (PCoA) aneurysm with a fistula to the cavernous sinus. This injury had been previously misinterpreted to be a PCoA aneurysm by computerized tomographic angiography (CTA). The patient was successfully treated with coils and Onyx of a fistula between the PCoA aneurysm and cavernous sinus