We present a case of carotid-cavernous fistula (CCF) in a 52-year-old female patient who was urgently referred for surgical treatment of a left-sided orbital phlegmon. On the 62nd day after a traumatic brain injury, the patient revealed a visual impairment of the left eye, which was noticeably red and showed a moderate protrusion. The patient’s left orbit was urgently opened and drained.She was undergoing an anti-inflammatory therapy and showed a positive dynamic of the disease, whilst on the 5th day after the procedure, the patient started feeling pain in the left eye and noise in the head. The data of ultrasound examination of the orbit and duplex scanning were largely consistent with a severe massive inflammatory infiltration of the retrobulbar tissue with hypervascularization (the orbital phlegmon could not be excluded). Only a selective computed tomography with angiography helped establish the final diagnosis: arteriovenous malformation in the projection of the supra-sphenoid section of the left internal carotid artery, with post-traumatic CCF on the left. After surgery (endovascular embolization of the CCF), a positive result was observed: with a positive result — no injection or pain in the left eye, exophthalmos gradually regressed. Yet the visual acuity of the left eye was 0.03 due to an atrophy of the optic nerve.Conclusion. The ophthalmologists must be on the alert in cases of unilateral exophthalmos with a history of blunt head trauma, since neuro-ophthalmic symptoms are crucial in clarifying the indications for a prompt implementation of the only surgical treatment effective for this pathology, i.e. endovascular embolization.