To scrutinize the economic impact of different care levels, such as shared care, in the follow-up of adult congenital heart disease (ACHD) patients. The BELgian COngenital heart disease Database combining Administrative and Clinical data (BELCODAC) was analyzed. Patients (N = 6579) were categorized into five care levels based on their cardiac follow-up pattern between 2006 and 2010. Medical costs, hospitalizations, and emergency department visits were measured between 2011 and 2015. In patients with moderate lesions, highly specialized cardiac care (HSC; exclusive follow-up by ACHD specialists) and shared care with predominantly specialized cardiac care (SC+) were associated with significantly lower medical costs and resource use compared to shared care with predominantly general cardiac care (SC-) and general cardiac care (GCC). In the patient population with mild lesions, HSC was associated with better economic outcomes than SC- and GCC, but SC+ was not. HSC was associated with fewer hospitalizations (- 33%) and less pharmaceutical costs (- 46.3%) compared to SC+. Patients with mild and moderate lesions in the no cardiac care (NCC) group had better economic outcomes than those in the GCC and SC- groups, but post-hoc analysis revealed that they had a different patient profile than patients under cardiac care. More specialized care levels are associated with better economic outcomes in patients with mild or moderate lesions in cardiac follow-up. Shared care with strong involvement of ACHD specialists might be a management option to consider. Characteristics of patients without cardiac follow-up but good medium-term economic prospects should be further scrutinized.