Support is needed for the well-being of nurses and first responders in external crises. We aimed to synthesize the evidence between workload management strategies and well-being of nurses, paramedics, and firefighters during external crises in an umbrella review. The data sources OVID Medline, APA PsycInfo, CINAHL, Web of Science and the Cochrane Library were searched between 1.1.2013-20.6.2023. Two independent reviewers assessed the eligibility of the publications and conducted the data extraction and narrative synthesis. The search identified 1,073 references on nurses and 182 on paramedics and firefighters. Of the 62 full texts, 16 systematic reviews on nurses were included, and of the 13 full texts on paramedics and firefighters, two systematic reviews were included, making a total of 18 systematic reviews. The quality of the publications was predominantly good (83%). Both employee and work-directed strategies were beneficial in supporting employee well-being during external crises. Proactive practical skills training and psychological interventions were found as the most promising employee-directed strategies. The corresponding work-directed strategies were effective communication, providing useful information and adequate working conditions, supportive leadership, and peer support. To support well-being of nurses and first responders during external crises, workload management strategies need to be proactively planned in workplaces.