Social science can serve national security practitioners by providing insights on best practices for interagency teams. The interagency team approach is an increasingly frequent recommendation for solving the much lamented problem of inadequate coordination and collaboration for national security. Historical examples indicate interagency teams can indeed be highly effective, but recent research at NDU also suggests that interagency team effectiveness is not widespread, easily replicated, or well understood. Greater use of interagency teams would be more likely and easier to execute if senior national security leaders knew with greater certainty what factors make these teams effective. This article points the way forward for more effective interagency teams by identifying their key performance variables, extracted from a review of the literature on organizational research of teams. Far from being a merely academic exercise, the authors show how insights from organizational research can produce immediate benefits for those interested in better interagency team performance.