The COVID-19 pandemic has demonstrated that emergency departments (EDs) need to reorganize their operations rapidly. This study investigated the impact of the pandemic on structural and logistical issues at EDs and the measures taken. Belgian EDs were surveyed on the implemented changes at the start of the pandemic in relation to the 4 S’s in disaster medicine: Structure, Staff, Supplies, and System. The study demonstrated that Belgian EDs felt largely unprepared for this pandemic, but nevertheless dynamically restructured their organization. A 46% increase in ED beds was created in different types of structures and more than 50% of all ED beds were reserved for COVID-19 care, but overall the number of patient presentations dropped by 29%. EDs deployed extra personnel, additional training, and psychological support. More than 50% reported an acute shortage of personal protective equipment, and several reported a shortage of ventilatory equipment and medications.