Abstract Introduction: A systemic venous source of pulmonary blood flow reduces the instability associated with Stage I Norwood physiology. We have previously demonstrated neonatal cavopulmonary assist under steady flow conditions. We hypothesized that pulsatile pulmonary perfusion would improve pulmonary hemodynamics. Methods: Lambs (7.2 +/− 1.1 SD kg, age 7.9 +/− 1.5 days) underwent cavopulmonary diversion using bicaval venous-to-main pulmonary artery cannulation. The proximal main pulmonary artery was clamped and the right ventricle vented for egress of coronary venous blood. A miniature centrifugal pump was used to assist cavopulmonary blood flow. Control animals (n = 4) underwent sham surgery. 13 animals received steady flow pulmonary perfusion, and six animals received pulsatile pulmonary perfusion. Hemodynamic and gas exchange data were measured for eight hours. Groups were compared using ANOVA. Results: All animals remained physiologically stable. Cardiac index, systemic arterial pressure, mean pulmonary arterial pressure, vena caval pressure, mean circulatory filling pressure, pO2, and pCO2 were not statistically different between the steady flow and pulsatile flow groups after 8 hours of cavopulmonary assist (P Conclusions: Pulsatile pulmonary perfusion yields a pulmonary vascular resistance comparable to control and lower than steady flow perfusion in a neonatal animal model of univentricular Fontan circulation.