This study evaluated the outcome of endovascular and conservative treatment for giant cavernous carotid artery aneurysms (CCAAs). We retrospectively reviewed a series of 35 consecutive giant CCAAs treated with endovascular and conservative treatment. All patients were evaluated by balloon occlusion test (BOT) before treatment. Patients who could tolerate BOT were treated by parent artery occlusion (PAO), those who could not tolerate BOT were treated by stent/coil or conservative methods. Eight patients were treated conservatively, symptoms were worsened in four patients (50%), unchanged in three, and improved in one at 33.6 +/- 19.9 months (6 similar to 65 months) follow-up. In 27 aneurysms treated with endovascular methods, 17 aneurysms were treated by PAO, eight aneurysms were treated with stent-assisted coil embolization, and two aneurysms were embolized with coils. The initial post-procedure angio gram revealed complete occlusion, neck remnant, and incomplete occlusion in 81.5 %, 11.1 %, and 7.4 %, respectively. Procedure-related mortality and morbidity were 0 and 7.4 %, respectively. At 33.1 +/- 17.4 months (4 similar to 71 months) follow-up, a good clinical outcome (mRS 0-1) was observed in 25 (92.6%) patients, symptoms were resolved or improved in 20 (74.1%). Statistical analysis showed that risk factors for poor clinical outcome included age of 60 years and older (P=0.006), and conservative treatments (P=0.038). Risk factors for poor clinical outcome of giant CCAAs included conservative treatment and age older than 60 years. A symptomatic giant cavernous carotid aneurysm should be treated. The outcome of endovascular treatment of giant CCAAs is promising.