Left atrial appendage (LAA) thrombus is a common finding in patients with atrial fibrillation and a major source of emboli that cause strokes. The incidental finding of an LAA thrombus during cardiac surgery is an infrequent finding during routine intraoperative echocardiography, and optimal management is not well defined. A case of a large, incidentally discovered LAA thrombus that became mobile on initiation of cardiopulmonary bypass in a patient undergoing coronary artery bypass graft surgery is presented. Intraoperative transesophageal echocardiography diagnosed the thrombus, discovered its dislodgement from the LAA, and very interestingly demonstrated its surgical removal. This case demonstrates the ability of intraoperative transesophageal echocardiography to alter surgical management and provides support for its routine use in cases in which LAA thrombi are likely.