Our goal was to develop a less invasive total cavopulmonary connection (TCPC) sheep model for testing total cavopulmonary assist (CPA) devices. Thirteen sheep underwent a right fourth intercostal lateral thoracotomy. In series I (n = 6), a polytetrafluoroethylene (PTFE) extracardiac conduit (ECC) was connected to inferior vena cava (IVC) and superior vena cava (SVC) by end-to-side anastomosis. The SVC/IVC remained connected to right atrium (RA). A PTFE graft bridged ECC to right pulmonary artery (RPA). Clamps between SVC/IVC anastomoses and RA diverted total venous blood to pulmonary circulation. In series II (n = 7), temporary bypasses between SVC/IVC and RA allowed SVC/IVC to be cut off from RA for better RPA exposure. The ECC-SVC/IVC were end-end anastomosed and ECC-RPA side-side anastomosed for total SVC/IVC to pulmonary artery (PA) conversion. In each series, one sheep died of bleeding. In five sheep in series I and six sheep in series II, the TCPC model was successfully created with significantly increased central venous pressure and significantly decreased PA pressure/arterial blood pressure. Our acute TCPC sheep model has a less traumatic right thoracotomy with no cardiopulmonary bypass and less blood loss with no blood transfusion, facilitating future long-term CPA device evaluation.