A 62-year-old woman with two vessel coronary artery disease was scheduled for an off-pump coronary artery bypass graft. Under general anesthesia, a 7.5 Fr pulmonary artery (PA) catheter (AH-05050-H, Arrow, USA) was inserted via an 8.5 Fr introducer in the right internal jugular vein. After several attempts, it was successfully guided into the PA, and the systolic/diastolic/mean pressure was 28/10/16 mmHg at 45 cm insertion. Since the catheter migrated into an overwedged position during the operation, the catheter was withdrawn several centimeter. After a while, a sudden change of PA pressure waveform to plateau was noticed, and then PA pressure fell into 0/0/0 mmHg. The PA catheter tip was seen protruding through the normal-appearing anterior wall of the right ventricle. The catheter was withdrawn to a right atrial position, and the perforation was closed. The operation was finished uneventfully and the patient remained stable for the next 14 days and was discharged home. In this case, withdrawal of the PA catheter probably placed its tip in the origin of the PA, from which it then slipped into and perforated the right ventricle. After withdrawal of a PA catheter to avoid an overwedged position, the balloon of the catheter should be re-advanced into a proper position or be withdrawn to a right atrial position.