The interface mechanism in a tsunami early warning system (TEWS) occurs between receiving tsunami information at the country level and disseminating warning and evacuation orders to the public. Three crucial actions take place during the interface: issuing the warning, disseminating it, and ordering an evacuation. Using two case studies in Indonesia and Sri Lanka, a study was undertaken to understand the nature of the interface mechanism and the social, cultural and political dynamics of its operationalisation. In this article, a comparative analysis of the two case studies is presented, focusing on the role of governance, institutions and people in this interface. The nature of governance, hierarchies and structures influence the interface mechanism and the associated decision-making mechanisms. The institutions who act as key stakeholders are also shaped by the governance structures and hierarchies within it. The efficiency of the institutions is determined by the nature of their human resources and are affected by political factors. The communities are also affected by the overall governance structure, the political dynamics and the institutional factors. The complex relationships between governance, institutions and officers that exist in the two countries affect the communities in different ways. Yet, the overall governance and institutional dynamics of TEWSs lead to a common thread of decisions and actions when operationalising the interface. The results are presented in a framework that illustrates the complex relationships between governance, institutions, officers and communities. The framework provides a basis for future research on how the interface of TEWS can be operationalised to effectively protect communities at risk from tsunami.