Endovascular cooling catheter-related thrombosis is an under-recognized clinical complication of targeted temperature management (TTM), which is widely used in the treatment of comatose out-of-hospital cardiac arrest survivors. A 16-year-old boy, who survived an out-of-hospital cardiac arrest, underwent TTM with an endovascular cooling system. A target temperature of 34°C was maintained for 24 hours, followed by rewarming at a rate of 0.5°C/12 hours. On day 5, his body temperature rose sharply after the removal of the endovascular cooling catheter. He was diagnosed with pneumonia and methicillin-resistant Staphylococcus aureus bacteremia. Tomography investigations also revealed a marked abnormality in the liver function. On day 7, a large thrombus extending through the right iliac vein and into the inferior vena cava (IVC) was detected. Owing to bacteremia, the IVC filter placement was not indicated, and the thrombus disappeared after intravenous administration of heparin and antithrombin. In addition to the potential risk of catheter-related thrombosis and hypercoagulability in the postcardiac arrest state, acute liver injury and an infective state may contribute to thrombosis.