Abstract Background Extracorporeal membrane oxygenation (ECMO) is a potential treatment option in critically ill COVID-19 patients suffering from acute respiratory distress syndrome (ARDS) if mechanical ventilation (MV) is insufficient; however, thromboembolic and bleeding events (TEBE) during ECMO treatment still need to be investigated. Methods We conducted a retrospective, single-center study including COVID-19 patients treated with ECMO. Additionally, we performed a univariate analysis of 85 pre-ECMO variables to identify factors influencing incidences of thromboembolic events (TEE) and bleeding events (BE), respectively. Results Seventeen patients were included; the median age was 57 years (interquartile range [IQR]: 51.5–62), 11 patients were males (65%), median ECMO duration was 16 days (IQR: 10.5–22), and the overall survival was 53%. Twelve patients (71%) developed TEBE. We observed 7 patients (41%) who developed TEE and 10 patients (59%) with BE. Upper respiratory tract (URT) bleeding was the most frequent BE with eight cases (47%). Regarding TEE, pulmonary artery embolism (PAE) had the highest incidence with five cases (29%). The comparison of diverse pre-ECMO variables between patients with and without TEBE detected one statistically significant value. The platelet count was significantly lower in the BE group (n = 10) than in the non-BE group (n = 7) with 209 (IQR: 145–238) versus 452 G/L (IQR: 240–560), with p = 0.007. Conclusion This study describes the incidences of TEE and BE in critically ill COVID-19 patients treated with ECMO. The most common adverse event during ECMO support was bleeding, which occurred at a comparable rate to non-COVID-19 patients treated with ECMO.