Teams have long been considered critical to the organizational structure of the military. The complex nature of military missions requires knowledge, skills, and abilities beyond those of a single individual, thus requiring the use of teams. Furthermore, the study of teams in the military environment is constantly evolving as the needs of the military and its missions change and adapt to new global circumstances. Psychology as a discipline has been particularly influential in addressing these needs, developing what is known regarding teams, their processes, training, and success in the military. Therefore, the purpose of this chapter is to review the science of teams and their effectiveness, extrapolate critical lessons learned, and highlight several future challenges critical for military psychology to address in order to prepare future military teams for success