Background: Congenital heart disease (CHD) is the most common type of birth defect. Survival, especially for patients with complex heart defects, has increased dramatically and today 97 % of those born with heart defects reach adulthood. As a late effect of both the congenital malformations and various types of interventions, these patients generally have an increased risk of atrial fibrillation, which is strongly associated with stroke. Addi-tionally, implantation of foreign materials such as mechanical heart valves is also associated with higher risk for embolization. Therefore, adult patient with congenital heart disease (ACHD) are at a substantially increased risk of thromboembolism which necessitates anticoagulant therapy. However, the impact and risk of bleeding and bleeding-related mortality, particularly in young ACHD patients, during long-term anticoagulation treatment is unclear.Methods: In this retrospective cohort study, 117 deceased ACHD patients with anticoagulant treatment were identified by using the Swedish registry of congenital heart disease between 2005 and 2021. Data from medical records were collected and analyzed. Variables obtained were main diagnosis, indication and type of anti-coagulation treatment, complications, and cause of death.Results: A total of 17 ACHD patients (14.5 %) experienced bleeding events. Ten ACHD patients (8.5 %) experi-enced major bleeding, including five patients (4.3 %) who died of a hemorrhagic stroke. Another seven ACHD patients had minor bleeding (6 %).Conclusion: Despite the occurrence of bleeding-related complications, the proportion of serious, fatal bleeding was low among deceased ACHD patients with anticoagulation treatment.