This report describes a 51-year-old man with rheumatoid arthritis, coronary artery disease, left ventricular failure, and saccular aneurysm of the left coronary cusp of the aortic valve. Rheumatoid arthritis can involve the heart in several ways; however, aortic valve aneurysm in rheumatoid arthritis has not been reported before. Absence of vegetation, lack of a history of infective endocarditis, and the preservation of aortic valve function suggested that this saccular aneurysm was not a result of infective endocarditis. An intimal flap, which strongly suggests aortic dissection, was not observed. To our knowledge, this may be a novel cardiac manifestation of rheumatoid arthritis, and this is the first published report.