Paradoxical embolism is an uncommon but increasingly reported cause of arterial embolic events. Involvement of the kidney is rarely reported. Autopsy studies suggest, however, that embolic renal infarction is underdiagnosed antemortem. We report a case of bilateral, main renal artery occlusion and acute renal failure secondary to paradoxical embolism. Clinical and laboratory data at presentation were not suggestive of renal infarction. Support for the diagnosis of paradoxical embolism, which most commonly occurs across a patent foramen ovale, was made by contrast echocardiography, which provides a sensitive method for detecting right-to-left intracardiac shunts. The often subtle presentation of renal infarction suggests patients with peripheral or central arterial embolic events should be carefully observed for occult renal involvement. Contrast echocardiography should be performed when renal infarction occurs without a clear embolic source to evaluate for paradoxical embolism.