Hemostatic disorders are common during extracorporeal membrane oxygenation (ECMO)-therapy. This includes both bleeding and thrombotic complications. Particularly bleeding is often associated with fatal outcome. The early identification of hemorrhagic diathesis and the diagnosis of the underlying pathology are essential. A distinction into device-, disease-, and drug-related disorders appears reasonable. However, both correct diagnosis and therapy can be challenging and sometimes counterintuitive. Since bleeding seems to be more frequent and dangerous compared to thrombosis, the understanding of coagulation disorders and minimizing anticoagulation has been focused in recent years. Due to progress in membrane coating and configuration of modern ECMO circuits it is even possible to perform ECMO without any anticoagulation in well selected cases. It became apparent that routine laboratory tests are likely to miss severe coagulation disorders during ECMO-therapy. Better understanding can also help to individualize anticoagulation in patients and hence preventing complications. Acquired von Willebrand syndrome, platelet dysfunction, waste coagulopathy as well as silent hemolysis should be taken into account when bleeding or thromboembolic complications appear. Recognizing impaired intrinsic fibrinolysis may favour intensified anticoagulation even in patients exhibiting signs of bleeding. Drug monitoring with standard coagulation tests, viscoelastic tests and anti-Xa-levels as wells as screening for disorders of primary hemostasis should be implemented in clinical routine to guide physicians through complex anticoagulative therapy. The patient's coagulative status should be interpreted taking the underlying disease and current therapy into account in order to enable a personalized approach to hemostasis in patients treated with ECMO.