Objective: Atrial septal aneurysm (ASA) is a localised “saccular” deformity of the interatrial septum, generally at the level of the fossa ovalis, which protrudes to the right or the left atrium or on both sides. It is a well recognised cardiac abnormality that was previously diagnosed on autopsy only, but it is now frequently picked up on routine echocardiography or during evaluation of ischemic stroke. There is a dearth of data on atrial septal aneurysm in our environment, and the authors set out to find the common cardiac abnormalities associated with atrial septal aneurysm in adults who had transthoracic echocardiographic examination in Enugu, South-East Nigeria Design and method: Conquest Medical Imaging is a private medical diagnostic centre in Enugu, South-East Nigeria. The centre offers radiologic and ultrasonography diagnostic services. The echocardiographic records of 1390 patients done over a 4-year period were retrospectively reviewed. The examinations were done with a Logic 500MD Echocardiographic machine made by General Electric. Data obtained from the echocardiography register included presence of atrial septal aneurysm, age, gender, other cardiac abnormalities present. Results: A total of 1174 adults had echocardiographic examination during the period under review, and consisted of 667 males and 507 females. The mean age of the males was 43.1 ± 6.2 years, while the mean age of the females was 45.9 ± 7.1 years. Atrial septal aneurysm was present in 28 patients representing 0.2% of the total adult population, and made up of 11 males and 17 females. 25 patients had one or more additional cardiac abnormalities, representing 89.3% of all patients with atrial septal aneurysm. Degenerative aortic valve disease, degenerative mitral valve disease, and left ventricular diastolic dysfunction were the cardiac abnormalities noted in addition. Conclusions: The frequent association of degenerative valvular heart diseases with atrial septal aneurysm in adults may suggest that atrial septal aneurysm has a degenerative aetiology in adults.