OBJECTIVE: Out-of-hospital cardiac arrest (OHCA) is a major public health challenge across Europe, with a survival rate of only 8.5% to hospital discharge. Implementing a community first responder (CFR) system, including earlier Basic Life Support and defibrillation, can enhance survival rates and neurological outcomes. This study assesses the cost-effectiveness of two scenarios for implementing such a system in Belgium. METHODS: A decision tree and the long-term Markov model were used to evaluate cost-effectiveness by comparing two scenarios with current care standards. Scenario 1 involved an awareness campaign on OHCA, while Scenario 2 included implementing a CFR system with automated external defibrillator (AED) integration, dispatch centre linkage and training for citizen responders. The analysis covered survival to the emergency department, hospital, discharge and neurologically intact survival, with sensitivity analyses to test robustness. RESULTS: The awareness campaign and implementation of the CFR system resulted in an incremental cost-effectiveness ratio of €14,976 and €16,442 per quality-adjusted life year gained for scenarios 1 and 2, respectively. Both scenarios showed improvements in survival rates at various stages, including hospital discharge and neurologically intact survival. CONCLUSION: This study highlights the benefits of enhancing Belgium's CFR for OHCA patients. It suggests that accessible AEDs, trained CFRs and an integrated emergency response system could improve survival rates and quality of life. These findings can guide policy and resource decisions, potentially improving the effectiveness and cost-efficiency of OHCA emergency services. Additionally, this approach could serve as a model for other regions aiming to strengthen their response to time-sensitive emergencies.