Abstract Background Univentricular heart (UVH) corrected with Fontan surgery may be associated with an increased risk of thrombosis. Data regarding optimal thrombotic prevention strategy after Fontan surgery in patients with UVH is scarce, and guidelines for antithrombotic treatment are not yet available. Purpose The aim was to evaluate the prevalence of antithrombotic treatments and their relation to mortality in patients with Fontan circulation. Methods A total of 5,075 patients with UVH were identified using data from the Swedish National Patient Register, the Cause of Death Register, and the National Prescribed Drug Register. Patients with UVH born in Sweden between 1970 and 2017 who underwent Fontan surgery were included. The study population was divided into three groups based on medication: anticoagulation therapy, antiplatelet therapy, and no therapy. Incidence rate (IR) was reported per 1000 person-years and calculated as the total number of deaths divided by total follow-up time. Confidence interval (CIs) for IR was estimated with Poisson regression. Kaplain-Meier was used to estimate the survival probability of 95% for UVH. The Stratified Cox proportional hazards model was used to estimate hazard ratios (HR) with 95% CI. Results The total cohort consisted of 864 patients of which 280 individuals (32%) had hypoplastic left heart syndrome (HLHS). The median follow-up time was 14.4 (IQR 3.9;24.9) years, maximum follow-up time was 47 years. Out of all the patients, 36% received no anticoagulation or antiplatelet therapy. Among those who did receive therapy, 75% were treated with antiplatelets. The patients who had no therapy had a higher mortality rate. During long-term follow-up, patients with UVH had higher survival rates when treated with antiplatelets. Conclusion Antithrombotic therapy, in particular antiplatelet therapy, was associated with the highest survival in patients with UVH as compared to no treatment. Our data suggest that antithrombotic treatment, and in particular antiplatelet treatment, could be considered in patients with UVH.Survival with Antithrombotic treatment