Extracorporeal membrane oxygenation (ECMO) is standard for cardiogenic shock, but outcomes remain limited. The BreathMo adult ECMO system with a maglev pump and a low-pressure drop oxygenator was developed. This report presents the 14 day in vivo early feasibility and preliminary safety of the ECMO system. In healthy ovine models (n = 10, weight range 54.3–76.8 kg), the investigational ECMO was instituted by venoarterial cannulation (n = 5) and venovenous cannulation strategy (n = 5). Pump flow rates were maintained around 1.5 L/min for partial support, and the gas flow rate was 1:1 to the blood flow rate with 50–80% oxygen concentration. Activated clotting times were mostly kept within the range of 140–200 seconds. Eight animals completed the intended study duration, while two had early termination. Post-oxygenator oxygen saturation remained above 95%, and arterial partial pressure of carbon dioxide (PCO₂) remained approximately 45 mm Hg during the study. Plasma-free hemoglobin values remained within the acceptable range. The two early terminations involved bleeding at the cannulation site and clinical deterioration with refusal to eat and inability to stand. No direct evidence of device malfunction or device thrombosis was identified in either case. The results support the early feasibility and preliminary safety of the BreathMo adult ECMO system under the tested experimental conditions.