The failing Fontan physiology may benefit from ventricular assist device (VAD) mechanical circulatory support, although a subpulmonary VAD placed at the Fontan connection has never successfully supported the Fontan circulation long term. The HeartWare CircuLite continuous flow VAD was examined for Fontan circulatory support in an in vitro mock circulation. The VAD was tested in three different scenarios: VAD in parallel, baffle restricted VAD in parallel, and VAD in series. Successful support was defined as simultaneous decrease in inferior vena cava (IVC) pressure of 5 mm Hg or more and an increase in cardiac output (CO) to 4.25 L/min or greater. The VAD in parallel scenario resulted in a CO decrease to 3.46 L/min and 2.22 mm Hg decrease in IVC pressure. The baffle restricted VAD in parallel scenario resulted in a CO increase to 3.9 L/min increase in CO and 20.5 mm Hg decrease in IVC pressure (at 90% restriction). The VAD in series scenario resulted in a CO of 1.75 L/min and 5.9 mm Hg decrease in IVC pressure. We successfully modeled chronic failing Fontan physiology using patient-specific hemodynamic and anatomic data. Although unsuccessful in supporting Fontan patients as defined here, the HeartWare CircuLite VAD demonstrates the possibility to reduce Fontan pressure and increase CO with a VAD in the Fontan connection. This study provides insight into pump performance and design issues when attempting to support Fontan circulation. Refinements in VAD design with specific parameters to help support this patient population is the subject of our future work.