Background In Germany, 70,000–100,000 persons per year suffer from out-of-hospital cardiac arrest (OHCA). Despite medical progress, survival rates with good neurological outcome remain low. For many important clinical issues, no or only insufficient evidence from randomised trials is available. Therefore, a systemic and standardised acquisition of the treatment course and of the outcome of OHCA patients is warranted. Study design The German Cardiac Arrest Registry (G-CAR) is an observational, prospective, multicentre registry. It will determine the characteristics, initial treatment strategies, invasive procedures, revascularisation therapies and the use of mechanical circulatory support devices with a focus on extracorporeal cardiopulmonary resuscitation. A special feature is the prospective 12-month follow-up evaluating mortality, neurological outcomes and several patient-reported outcomes in the psychosocial domain (health-related quality of life, cognitive impairment, depression/anxiety, post-traumatic stress disorder and social reintegration). In a pilot phase of 24 months, 15 centres will include approximately 400 consecutive OHCA patients ≥ 18 years. Parallel to and after the pilot phase, scaling up of G-CAR to a national level is envisaged. Conclusion G-CAR is the first national registry including a long-term follow-up for adult OHCA patients. Primary aim is a better understanding of the determinants of acute and long-term outcomes with the perspective of an optimised treatment. Trial registry NCT05142124. Graphical abstract German Cardiac Arrest Registry (G-CAR)