A deliberate attack involving chemical, biological, radiological, or nuclear (CBRN) material has the potential to cause substantial fear among the public. This presents problems for communicators, who will need to provide information quickly after an attack while ensuring that their messages are easily understood and likely to be attended to by members of the public. Identifying in advance what people would want to know, where they would get information from, and how messages should be presented might allow communicators to ensure that their messages have the best chance of having their desired effect. In this review, we identified all peer-reviewed studies that have assessed communication strategies or information needs using hypothetical CBRN scenarios or in actual CBRN incidents. We identified 33 relevant studies. Their results support existing psychological models of why people engage in health protective behaviors, with information about the severity of the incident, the likelihood of being exposed, the efficacy and costs or risks of recommended behaviors, and the ability of individuals to perform recommended behaviors being sought by the public. Trust plays a crucial role in ensuring that people attend to messages. Finally, while a large variety of spokespeople and sources were identified as being turned to in the event of an incident, the use of multiple information sources was also common, affirming the importance of communicating a consistent message through multiple channels. Further research is required to extend these predominantly US-based findings to other countries and to confirm the findings of research using hypothetical scenarios.