Coordination theories are characterized primarily by a focus on integration, in which coordination is aimed at achieving a coherent and unified set of actions. However, in the extreme settings in which fast-response organizations operate, achieving integration is often challenging. In this study we employ a fragmentation perspective to show that dealing with ambiguity and discontinuity is not only inevitable for these organizations, it is a key characteristic of coordinating. We undertook an inductive, qualitative field study on how officers in command from the fire department, medical services, and police coordinate during emergency response operations. Our data are based on a four-year multi-site field study of 40 emergency management exercises in the Netherlands, combined with 56 retrospective interviews. Our inductive analysis of this data shows that officers use three coordination practices to deal with ambiguity and discontinuity: working around procedures, delegating tasks, and demarcating expertise. We theorize our findings by showing how these practices lead to conditions in which fragmentation can become an effective method of coordination. In doing so, we provide a more complete understanding of the process of coordinating in fast-response settings that will benefit both crisis management practice and organizational theory.