Background: A progressively increasing prevalence of congenital heart disease (CHD) in adulthood has been noticed in recent decades; CHD cases with a systemic right ventricle have a poorer outcome. Methods: Seventy-three patients with SRV evaluated in an outpatient clinic between 2014 and 2020 were enrolled in this study. Thirty-four patients had a transposition of the great arteries treated with an atrial switch operation; 39 patients had a congenitally corrected transposition of the great arteries (ccTGA). Results: Mean age at the first evaluation was 29.6 ± 14.2 years; 48% of the patients were female. The NYHA class at the visit was III or IV in 14% of the cases. Thirteen patients had at least one previous pregnancy. In 25% of the cases, complications occurred during pregnancy. Survival free from adverse events was 98.6% at one year and 90% at 6-year follow-up without any difference between the two groups. Two patients died and one received heart transplantation during follow-up. The most common adverse event during follow-up was the presence of arrhythmia requiring hospitalization (27.1%), followed by heart failure (12.3%). The presence of LGE together with lower exercise capacity, higher NYHA class and more dilated and/or hypokinetic RV predicted a poorer outcome. Quality of life was similar to the QoL of the Italian population. Conclusions: Long-term follow-up of patients with a systemic right ventricle is characterized by a high incidence of clinical events, prevalently arrhythmias and heart failure, which cause most of the unscheduled hospitalizations.