Goal: Resuscitative endovascular balloon occlusion of the aorta (REBOA), originally designed to block blood flow to the distal part of the aorta by placing a balloon in trauma patients, has recently been shown to increase coronary perfusion in cardiac arrest patients. This study evaluated REBOA in increasing the aortic pressure and coronary perfusion pressure (CPP) in non-traumatic out-of-hospital cardiac arrest (OHCA) patients. Methods: Adult OHCA patients with cerebral performance category 1 or 2 prior to cardiac arrest, and without evidence of aortic disease, were enrolled from Jan. to Dec. 2021. Aortic pressure and right atrial pressure were measured before and after balloon occlusion. CPP was calculated using the measured aortic and right atrial pressures, and the values before and after the balloon occlusion were compared. Results: Fifteen non-traumatic OHCA patients were enrolled in the study. The median call to balloon time was 46.0 (IQR, 38.0-54.5) min. The median CPP before and after balloon occlusion was 13.5 (IQR, 5.8-25.0) and 25.2 (IQR, 12.0-44.6) mmHg, respectively (P=0.001). The median increase in the estimated CPP after balloon occlusion was 86.7%. Conclusion: The results of this study suggest that REBOA may increase the CPP during cardiopulmonary resuscitation (CPR) in patients with non-traumatic OHCA.