Renal artery thrombosis is a rare vascular event that precipitates renal infarction. Although in up to one third of cases the etiology is not identified, renal artery lesions, cardioembolism and acquired thrombophilias are the main causes. A bilateral simultaneous idiopathic renal artery thrombosis is an unlikely coincidence. We present two cases of patients with acute bilateral renal artery thrombosis of unknown etiology. Cardiac embolism, acquired thrombophilia and occult neoplasm workups were negative. Both cases were temporarily hemodialysis-dependent and partially recovered renal function under conservative approach with systemic anticoagulation. Recommendations on optimal treatment for renal artery thrombosis are still lacking. We discuss the available options.