Preparing for a potential bioterroism is a difficult task for health care leaders because of the fundamental unpredictability of bioterroist acts. Complexity science thinking is presented as an approach that can help in this task. Basic concepts from complexity science, especially the role of relationships, are presented. Specific recommendations for action including sensemaking, learning, and improvisation are made. A case study is used to illustrate the power of complexity science thinking in assisting health care leaders addressing potential bioterroism. Questions for further research are presented.