Free-floating intracardiac thrombi represent a severe yet uncommon condition and mostly coexist with thromboembolism. Notably, mobile right heart thrombus can occur in patients with massive pulmonary embolism. Early diagnosis and management can be life-saving. Spontaneous atrial thrombosis due to restrictive cardiomyopathy has also been rarely reported. We describe here an unusual case of free-floating biatrial thrombi with concomitant saddle pulmonary embolism in a patient with idiopathic restrictive cardiomyopathy and sinus rhythm who had lower extremity deep vein thrombosis following the left knee arthroplasty. In the absence of treatment, mortality from pulmonary embolism remains high. Nevertheless, in our patient, blood stasis with dilated atria, resulting from restrictive hemodynamics, and deep venous thrombosis were the most likely causes for the formation of biatrial thrombi and concomitant pulmonary embolism. (C) 2008 Elsevier Ireland Ltd. All rights reserved.