It is unclear whether patients with adult congenital heart disease (ACHD) should be considered as an increased risk population with poor outcomes when suffering from COVID-19. This study aimed to collect clinical outcome data and to identify risk factors of a complicated course of COVID-19 among ACHD patients. Among all outpatients who came to medical attention via telemedicine or direct physician contact at our institution between September 1, 2020 and March 31, 2021, we included all with a COVID-19 diagnosis. The incidence of COVID-19, a clinical course of the disease, and outcome were determined. One hundred and four (8.7%) out of 1 197 patients who were seen at our outpatient clinic for ACHD patients met the definition of COVID-19. Most of them reported a mild course of COVID-19 (99 [95.5%]). Five patients (4.5%) experienced severe symptoms and needed hospitalization. Two patients (1.9% of all with a confirmed diagnosis, 40% with severe infection) died. In the multivariable analysis, decreased systemic ventricular systolic function and any significant valve stenosis were predictors of a complicated disease course. Our study confirmed previous results showing that a physiology-based model, rather than an anatomy-based model, better predicted COVID-19 outcomes among ACHD patients, which is of importance for patients and healthcare providers during the COVID-19 pandemic.