This article describes the origins and contributions of the naturalistic decision making (NDM) research approach. NDM research emerged in the 1980s to study how people make decisions in real-world settings. The findings and methods used by NDM researchers are presented along with their implications. The NDM framework emphasizes the role of experience in enabling people to rapidly categorize situations to make effective decisions. The NDM focus on field settings and its interest in complex conditions provide insights for human factors practitioners about ways to improve performance. The NDM approach has been used to improve performance through revisions of military doctrine, training that is focused on decision requirements, and the development of information technologies to support decision making and related cognitive functions.