There are few observation papers regarding the natural history of an aneurysm. We report on a case of a completely occluded middle cerebral artery (MCA) aneurysm. A 47-year-old female patient presented with a headache and was diagnosed with rupture of a right MCA aneurysm. Due to a high risk of direct neck clipping, she received conservative treatment after craniotomy and wrapping of her aneurysm. The patient's condition showed improvement, with complete occlusion of the aneurysm and considerable reduction of the aneurysm in size after approximately three years. This is a rare case of an aneurysm of MCA that showed spontaneous resolution. Finally, on the angiogram, characteristics of an aneurysm to occlude spontaneously will be presumed based on literature reviews.