Key PointsQuestionWhat is the association between socioeconomic position (SEP) and survival after out-of-hospital cardiac arrest (OHCA), and what are possible underlying mechanisms?FindingsIn this cohort study of 121 516 Korean adults with OHCA, lower SEP was associated with lower odds of survival to discharge. The mediation proportions for witnessed status, bystander cardiopulmonary resuscitation, and emergency department level in all patients were 15.1%, 4.8%, and 9.4%, respectively, while those for coronary angiography and targeted temperature management in admitted patients were 20.2% and 4.2%, respectively.MeaningThese findings suggest that public health interventions targeting potentially modifiable mediators can be implemented to reduce disparities in survival among patients with OHCA with different SEP.