An 80-year-old female was admitted to our hospital with diplopia that had first appeared 3 weeks previously. She did not complain of headache, ocular pain, or tinnitus. A neurologic examination revealed limitations in lateral gaze in the left eye, which suggested left abducens nerve palsy (Fig. 1A). No other abnormalities were found in cranial nerve examinations, such as in pupil size or light reflex. We performed serologic testing, including complete blood count, hemoglobin A1C, and the thyroid function test, and the results were within the normal limits. The patient underwent brain magnetic resonance imaging, which revealed a large cavernous aneurysm in the left internal carotid artery (ICA) originating at the left cavernous sinus (Fig. 1B). This aneurysm compressed the cavernous sinus segment of the left abducens nerve, causing abducens nerve palsy. Digital subtraction angiography confirmed a 2.37 × 1.71 cm aneurysm in the cavernous portion of the left ICA (Fig. 1C). The patient underwent coil embolization using the stent-assisted technique, and her gaze symptom had improved 4 months later.