The aim of this paper was to investigate experts' perceptions on communication in chemical, biological, radiological and nuclear (CBRN) terrorism crises, including challenges and good practices. This is pursued by means of a qualitative online questionnaire aimed at international crisis communication and crisis management experts. The challenges of communication concerning CBRN terrorism arise from the complexity of such incidents, having to do with the nature of the threat, leading to problematic public perceptions and response. Critical areas that need to be taken into consideration include resources, competences, and cooperation in preparedness communication and when providing information during a crisis. The findings and conclusions of this study will serve the development of an audit instrument for communication preparedness towards CBRN terrorism.