Abstract: Aims The coronavirus disease-2019 (COVID-19) pandemic poses significant challenges to many groups within societies, and especially for people with chronic health conditions. It is, however, unknown whether and how the pandemic has thus far affected the physical and mental health of patient populations. Therefore, we investigated how the pandemic affected the lives of adults with congenital heart disease (CHD), compared pre- and peri-pandemic patient-reported outcome measures (PROMs) and a patient-reported experience measure (PREM), and investigated whether having had COVID-19 impacted pre-/peri-pandemic differences of the PROMs and PREM. Methods and results As part of the ongoing APPROACH-IS II project, we longitudinally surveyed 716 adults with CHD from Belgium, Norway, and South Korea. Pre-pandemic measures were administered from August 2019 to February 2020 and the peri-pandemic surveys were completed September 2020-April 2021. The majority of patients indicated that their social lives (80%), mental health (58%), and professional lives/education (51%) were negatively impacted by the pandemic. Patients felt worried (65%), were afraid (55%), reported the pandemic felt 'close' to them (53%), and were stressed (52%). However, differences between pre- and peri-pandemic scores on the PROMs and PREM were negligibly small (Cohen's d < 0.20). Across measures, 5.8-15.8% of patients demonstrated changes (improved or worsened scores) that exceeded the minimal clinically important difference. There were no difference-in-differences for PROMs and PREM between patients who did vs. did not have COVID-19. Conclusions Although the COVID-19 pandemic has been disruptive in many ways, pre- to peri-pandemic changes in PROMs and PREM of adults with CHD were negligibly small.