A right atrial thrombus in structurally normal heart is very rare. A 66-year-old woman was admitted with chest discomfort and dyspnea. She was diagnosed of right atrial myxoma on echocardiography and chest computed tomography, We peformed an excision of the mass attached to atrial septum, which was found to be an organized mural thrombus by pathologic examination. We report this rare case with a review of literature.