Purpose To describe survival and morbidity among children requiring extracorporeal membrane oxygenation (ECMO) after cardiac surgery. Methodology Retrospective single-centre cohort study of patients aged less than 18 years undergoing cardiac surgery between 2013 and 2021 at Queensland Children’s Hospital. Only patients who required post-operative ECMO in the same admission as their index surgical procedure were included. Patient information was obtained from the Australia and New Zealand Congenital Outcomes Registry for Surgery (ANZCORS) and hospital records. Morbidity endpoints included the need for new mobility aids postoperatively, new neurological deficit, developmental impairment, growth restriction (weight or height < 5th percentile for age), home oxygen support, invasive feeding and long-term renal replacement therapy. Results Of 2,227 children who underwent a cardiac surgical procedure, 66 (3%) required post-operative ECMO during the study period. Median age was 34.5 days (IQR 10.5-133.8 days) and median weight was 3.75kg (IQR 3.1-4.9kg). 51 patients (77.3%) had a biventricular circulation. 15 patients had (22.7%) had single-ventricle physiology. 97% received venoarterial ECMO. The most common indications for ECMO were failure to wean from cardiopulmonary bypass (n=25, 37.9%) and postoperative cardiac arrest (n=20, 30.3%). Median duration of ECMO was 5.5 days (IQR 3-10.8 days). 38 patients (57.6%) survived to hospital discharge. Median follow-up was 5 years (IQR 3.2-6.9 years). Kaplan-Meier survival in the overall study cohort was 57.6% at 1 year and 51.1% at 5 years. Among survivors to discharge, survival was 97.4% at 1 year and 88.7% at 5 years. Major morbidity was observed in 21 hospital survivors (55.3%) during follow-up. Conclusion Children who require ECMO after cardiac surgery have high hospital mortality with low attrition after discharge. Nearly 90% of hospital survivors are alive at 5 years. However, major morbidity persists in more than 50% of survivors.