BACKGROUND: The outcomes of patients with nonshockable out-of-hospital cardiac arrest (OHCA) are poor, but may be improved by extracorporeal cardiopulmonary resuscitation (E-CPR). OBJECTIVE: To examine the effects of veno-arterial extracorporeal membranous oxygenation (ECMO) as E-CPR in patients with nonshockable OHCA after emergency medical services (EMS) arrival for whom satisfactory cardiopulmonary resuscitation (CPR) was immediately performed. METHODS: Among 16,452 patients enrolled in the SOS-KANTO 2012 study, we examined data on 531 patients aged ≥ 18 years who performed activities of daily living (ADL) well or had moderate disability before the onset of cardiac arrest (CA) and those with normal spontaneous respiration or pulse palpation upon EMS arrival. CPR was performed immediately after CA onset, and advanced life support was provided upon hospital arrival for these patients. We divided patients into ECMO and non-ECMO groups. We retrospectively analyzed background factors and clinical outcomes. RESULTS: E-CPR was performed on 38 (7.2%) patients. In the univariate analysis, the mean age of the ECMO group was lower, ADL function before onset was more favorable, mean body weight was higher, and the mean interval from onset until hospital arrival was shorter than those in the non-ECMO group. One-to 3-month survival or favorable cerebral function outcome rates were higher in the ECMO group than in the non-ECMO group. In the multivariate analysis, ECMO use and the interval from onset until hospital arrival were independent prognostic factors for favorable cerebral functional outcomes at 1 and 3 months. CONCLUSION: E-CPR may be associated with favorable outcomes in carefully selected patients with nonshockable OHCA.