An atrial septal aneurysm is well recognized abnormality of uncertain clinical relevance. An intraatrial aneurysm was demonstrated in the fossa ovalis of a 41-year-old woman who suffered an episode of cerebellar infarction with recurrent atrial fibrillation. The disorder is rarely treated surgically. Most patients with this condition are given life-long anticoagulation, a treatment that may have serious complications. We report a rare case of atrial septal aneurysm with recurrent atrial fibrillation and cerebellar infarction which receiving an appropriate diagnosis and curative treatment.