Acts of terror may be characterized as violent extremism. Increasingly, these acts occur outside of the context of military conflict. The last two decades in particular demonstrate that urban trauma and violent extremism have substantial overlap in the way that individuals are injured and the care that is required. Accordingly, population dense locales must prepare to address severe injuries, profound chaos, and ongoing threats to health and welfare including urban infrastructure and access to medical care that arise around violent extremist actions. Coordinating pre-hospital and in-hospital healthcare and law enforcement resources represents a readily deployable approach to improving outcomes from such events. Since violent extremism continues to plague both the USA and countries around the globe, understanding the ways that healthcare systems, law enforcement systems, and individuals (both trained and untrained) prepare for urban trauma and terror events and share best practices is highly relevant. This chapter explores those preparations and practices, highlights the disruptive elements shared by conventional urban trauma and violent extremism, and underscores how paradigm shifts in terrorism have driven the changing profile of Emergency Medical Systems (EMS) and trauma system (TS) responses to both injury and extremism.