A pulmonary artery catheter (PAC) is a useful monitoring device for measuring pulmonary artery pressure, pulmonary capillary wedge pressure and cardiac output, but its insertion brings about many complications including pulmonary artery rupture, infarction, thrombosis and infection. This case concerns the knotting of a PAC in a 27 year-old female patient who had undergone cardiac transplantation due to dilated cardiomyopathy. The PAC was inserted via the right subclavian vein to the pulmonary artery and withdrawn to the superior vena cava before heart was removed. After the weaning of the cardiopulmonary bypass (CPB), we tried to reinsert the PAC, which was neither advanced nor withdrawn. Postoperative chest x-ray revealed that the PAC appeared to be knotted in the subclavian vein. Two days later, we loosened the knot of the PAC and removed it via femoral and bracheal cineangiography techniques guided by fluoroscopy without any complications. In this case, we thought the knotting of the PAC occurred at insertion due to severe tricuspid regurgitation, and its size was reduced at withdrawal before the CPB and wedging to the subclavian vein. Knotting of PAC is very rare and unpredictable, but once it or other complications of the PAC is suspected, we recommend that the manipulation of the PAC should be stopped and x-ray should be checked.