BACKGROUND: Young people with congenital heart disease (CHD) are frequently affected by discontinued follow-up when transferring from paediatric to adult care. Identified predictors for discontinuation include mostly patient-related factors, and further knowledge of hospital and healthcare system factors is needed. AIM: This study aims to explore patient-related, hospital-related and healthcare system-related factors affecting continued follow-up care after transfer, as perceived and experienced by paediatric cardiology and adult CHD (ACHD) healthcare providers (HCPs) in Sweden and Belgium. METHODS: This descriptive qualitative study included individual interviews with cardiologists, nurses and administrative staff, subjected to qualitative content analysis. A total of 30 HCPs from 13 specialist care outpatient clinics at 8 different centres in Sweden and Belgium were interviewed. HCPs were included if they had direct contact with patients and had at least 1 year of work experience. FINDINGS: The findings illuminate three main categories of factors perceived by HCPs to affect continued follow-up care after transfer, including 'care structure', 'care processes' and 'patient characteristics and circumstances'. Success was described as multifactorial, emphasising processes and structures of care, with a focus on collaboration, organisation, joint responsibility, resources, care relationships and transitional care interventions. Few differences appeared between paediatric and ACHD HCPs and between Swedish and Belgian HCPs. CONCLUSION: HCPs perceived factors on patient, hospital and healthcare system levels to influence continued follow-up. Process-related and structure-related aspects of care were perceived as more influential than individual patient characteristics. Hence, future research on discontinued follow-up care should focus on process-related and structure-related aspects of care delivery.