Iatrogenic pseudoaneurysms are extremely rare in children. Conventional management of pseudoaneurysms in adults has included surgical repair, ultrasound-guided compression, and more recently, endovascular embolization. However, in infants and children, there is little information regarding the applicability of such treatment modalities, which have been effective in adults, because of its rarity. Here, we present the case of a 6-month-old infant who developed a postprocedural pseudoaneurysm of the external iliac artery, which was successfully treated with ultrasound-guided percutaneous thrombin injection.