Anticoagulation for thromboembolic disease and bleeding, the main complication of anticoagulation therapy, are uncommon but are potentially life- or limb-threatening conditions that may present in the pediatric emergency department. Thromboembolic disease in children usually occurs as a complication of vascular access, primarily in children with congenital heart disease or cancer. However, complications of anticoagulation therapy used in the treatment of venous thromboembolism, pulmonary embolism, and blocked central venous catheter; arterial thromboembolism, including arterial ischemic stroke, Kawasaki disease, and after cardiac surgery, may warrant a visit to n the pediatric emergency department. Anticoagulation therapy may take the form of unfractionated heparin, low-molecular weight heparin, vitamin K antagonists, acetylsalicylic acid, or thrombolytic therapy. Monitoring anticoagulation therapy in children is very important and follows adult guidelines. Anticoagulant dosing may be adjusted based on activated partial thromboplastin time, anti-factor Xa level, and international normalized ratio.