A 30 year old, otherwise healthy man presented with flank pain and was ultimately found to have a rightsided renal infarction. Transthoracic echocardiography suggested, and then transesophageal echocardiography (TEE) confirmed, the presence of cor triatriatum sinister. Given the lack of other sources of emboli, this was felt to be the most likely source. We describe the case and both the echocardiographic and CT findings of this rare condition. This case demonstrates the need for TEE in some cases where 2D echocardiography is not sensitive enough to "rule out" cardio-embolic sources. This is only the second case in the literature of a systemic embolization due to cor triatriatum, and the first one in the Western literature.