Infrequently, patent foramen ovale or atrial septal defect act as a passage for the venous thrombi to reach the arterial circulation. These arterial thrombi can evoke tragic paradoxical embolisms. We report a case of impending paradoxical embolism due to a huge thrombus trapped through a patent foramen ovale in a 66-year-old man who presented with sudden dyspnea and chest discomfort in ten days after colon cancer surgery. The transthoracic echocardiogram demonstrated signs of acute right ventricular pressure overload and a huge linear mass wedged in a patent foramen ovale. On the intraoperative transesophageal echocardiography, the huge linear mass was freely floating in both right and left cardiac chambers passing through atrial septum. To prevent paradoxical embolism from this thrombus, he underwent emergent embolectomy and about 25 cm sized linear thrombus entrapped PFO was successfully removed.