The nature of humanitarian response has evolved in response to increasing humanitarian needs, number and scale of emergencies, and the expansion of certified Emergency Medical Teams. This research examines the International Federation of Red Cross and Red Crescent Societies' clinical and public health Emergency Response Units in emergencies from 2015 through 2019 using a mixed methods approach, consisting of a desk review and primary qualitative data, to inform prioritization of response activities and optimization of health surge support in emergencies. Identified opportunities for improvement include needs assessment, increased modularity, context-appropriate support/integration, human resources and capacity building, monitoring and evaluation, and the overall nature of health surge response to various emergency types. Greater focus on public health response; standardizing deployment criteria, standard operating procedures, and monitoring for clinical surge support; and regional and local capacity building could all improve health service quality and sustainability and facilitate more cost-effective emergency response.