BACKGROUND: We analyzed bleeding and thrombotic complications in COVID-19--associated ARDS requiring extracorporeal membrane oxygenation (ECMO). METHODS: This was a single-center observational study of adult subjects undergoing ECMO for COVID-19 (n = 67) or all other cause of ARDS (n = 60), excluding trauma patients. RESULTS: In the COVID-19 group, duration of invasive mechanical ventilation prior to ECMO was lower (2 [0-4] d vs 3 [1--6] d) and ECMO retrieval less frequent (71% vs 87%). No significant differences were found in Simplified Acute Physiology Score II, Acute Physiology and Chronic Health Evaluation II (APACHE II), or in the in-hospital survival predicted by the Respiratory ECMO Survival Prediction score. During the first 7 d of ECMO support, the COVID-19 group presented higher platelets and fibrinogen, lower activated partial thromboplastin time, but no differences in D-dimer. Thrombotic complications were similar between groups. Higher rates of severe bleeding, namely airway bleeding (37.3% vs 15.0%) and hemothorax (13.4% vs 3.3%), were found in COVID-19, with lower hemoglobin and higher red blood cell transfusions. COVID-19 ARDS was associated with longer ECMO duration (47 [17-80] d vs 19 [12-30] d) and absence of a statistically significant difference concerning in-hospital mortality. CONCLUSIONS: COVID-19--associated ARDS requiring ECMO presented high rates of severe bleeding complications and a protracted course. Further studies are needed to clarify the risks and benefits of ECMO in severe COVID-19--associated ARDS. [ABSTRACT FROM AUTHOR]