Background:Mass casualty incidents (MCIs) place extraordinary demands on healthcare systems, requiring rapid prioritization of patients when available resources are insufficient. In Sweden, the absence of a unified national mass casualty triage system has been identified as a challenge for effective coordination across prehospital and intrahospital settings. Objective:To achieve expert consensus on criteria for a national Swedish mass casualty triage system and to identify a suitable framework and triage algorithm that can be implemented consistently across the healthcare continuum. Results:A structured Delphi methodology was applied during a national consensus workshop involving multidisciplinary experts from healthcare, emergency services, authorities, and relevant organizations. Consensus was reached on 34 statements forming the basis of the Swedish Model Uniform Core Criteria (SMUCC). The criteria emphasize simplicity, rapid applicability, adaptability to all age groups and incident types, and use in resource-limited environments. Consensus supported the use of identical primary triage algorithms in prehospital and intrahospital settings, reliance on yes/no criteria rather than vital sign measurements, and inclusion of defined life-saving interventions. Among evaluated systems, SALT (Sort–Assess–Life-saving interventions–Treatment/Transport) was ranked as the most suitable foundation for a national system, with potential modifications aligned to SMUCC. Conclusions:There is broad national expert consensus that Sweden should implement a unified mass casualty triage system. The SMUCC framework provides a scientifically and professionally grounded basis for such implementation, with SALT identified as the most compatible existing system. Further work is required to address unresolved ethical and operational issues, particularly regarding the potential use of an additional “expectant” triage category.