Various thrombo-embolic complications have been related to the antiphospholipid syndrome. The authors report the case of a patient with a primary antiphospholipid syndrome associated with a right auricular mass highly suggesting a myxoma by both echocardiography and nuclear magnetic resonance imaging. Meanwhile, the histological examination of the operative specimen showed a well organized and calcified thrombus. Intracardiac thrombus has been rarely reported as a complication of the antiphospholipid syndrome. The preoperative investigations can't differentiate such a thrombus with a myxoma and the diagnosis is usually made postoperatively.