This paper presents a brief history of psychology and psychiatry roles in psychological selection and how these roles have evolved into the Behavioral Sciences Branch at the Johnson Space Center USC), Houston, TX. Since the initial selection of the Mercury Seven, the first United States astronauts, psychologists and psychiatrists have been involved in astronaut selection activities. Initially very involved in psychological selection of astronauts, the role of behavioral health specialists waned during the Gemini and Apollo years. With the onset of the NASA/Mir/International Space Station Program, the introduction of payload and mission specialists, and international collaboration, the evolving need for behavioral health expertise became apparent. Medical and psychological selection processes were revisited and the Johnson Space Center developed a separate operational unit focused on behavioral health and performance. This work unit eventually became the Behavioral Sciences branch of the Space Medicine and Health Care Systems Office. Research was allocated across groups at JSC, other NASA space centers, and the National Space Biomedical Research Institute, and was funded by NASA Headquarters. The current NASA focus on human space exploration to the Moon and beyond re-emphasizes the importance of the human-centered approach.