One of the most crucial issues in emergency systems is the readiness of emergency medical services for mass casualty situations. An unexpected catastrophe involving multiple injured people that overwhelms the local healthcare system is known as a mass casualty incident. To create a conceptual model, this study sought to determine and verify the elements of emergency medical services preparedness in mass casualty situations. Methods: This study used a mixed-method explanatory approach. Based on the PRISMA guideline, a systematic study was first conducted to identify the elements of emergency medical services preparation in mass casualty scenarios. Second, utilizing in-depth semi-structured interviews and the content analysis method, a qualitative study was created to investigate the components of readiness. Third, an expert panel integrated the elements taken from the two stages of the qualitative investigation and systematic review. Fourth, the Delphi method was used to validate the components that were retrieved. In the Delphi phase, two rounds were completed. Lastly, a group of experts created the conceptual model of emergency medical services readiness in mass casualty situations. Conclusions: Planning and managing mass casualty crises requires an integrated framework and model of emergency medical service preparedness. The components and final model of this study, which can be utilized as a plan to enhance emergency medical service preparation in response to mass casualty crises, were acquired following the methodical scientific steps.