BACKGROUND: The HeartMate 3 ventricular assist device (VAD) is a newer centrifugal continuous-flow VAD used for bridge-to-transplant and destination therapy in adults. However, there is limited experience regarding its use in children and adults with complex congenital heart disease (CHD). METHODS: The Advanced Cardiac Therapies Improving Outcomes Network (ACTION) is a multicenter learning network comprised of pediatric hospitals implanting VADs in children and adults with complex CHD. We examined the outcomes of patients undergoing HeartMate 3 implantation at an ACTION center between December 2017 and September 2019. RESULTS: The HeartMate 3 was implanted in 35 patients at 9 ACTION centers, with a median age of 15.7 (8.8-47.3) years, median weight of 65.7 (19.1-114.1) kg, and median body surface area (BSA) of 1.74 (0.78-2.36) m(2). Of the cohort, 14 patients (40%) weighed <60 kg. Diagnoses included dilated cardiomyopathy (63%), dilated cardiomyopathy in neuromuscular disease (20%), and CHD (17%). Of those with CHD, most had a Fontan circulation. With a median 78 days of follow-up, there was 1 death on device (97% survival); 20 out of 35 (57%) underwent transplantation with no post-transplantation mortality. There were no episodes of stroke or pump thrombosis. CONCLUSIONS: Use of the HeartMate 3 in ACTION centers was associated with a low incidence of mortality and adverse events. Patients as small as 19 kg (BSA 0.78 m(2)) were successfully implanted and supported, indicating that this device may be appropriate for older children and small adults.