Acts of terrorism can be harrowing and cause extensive damage, yet they occur far too frequently. How do terrorist groups organize and coordinate their attacks? What makes those groups simultaneously cohesive and flexible in a hostile environment? Different academic disciplines have contributed to a better understanding of the proliferation of terrorist acts in recent years. With very few exceptions, however, extant psychological research on terrorism has almost exclusively focused on the individual terrorist. We leverage the team literature to better understand how a team of terrorists radicalizes, organizes, and makes decisions. Drawing from the work of Weick (1976), we characterize terrorist teams as loosely coupled systems. Examples of different terrorist attacks from the last 15 years illustrate how loose coupling in terrorist teams is especially powerful because of the high familiarity and intimacy among members of terrorist teams. Loosely coupled structures have led to highly adaptive and resilient teams whose actions are fluid, unpredictable, and often lethal. We conclude by discussing implications for counterterrorism and for future research.