This article offers a historical perspective on the contributions of the field of psychology and the American Psychological Association (APA) to the public policy arena. It traces APA’s involvement from a 1956 Council of Representatives resolution on the application of psychology to inform public policy to current advocacy initiatives related to psychological science, practice, and education in the public interest. Attention is directed to APA’s early policy structures together with the development of affiliated state, provincial, and territorial psychological associations and the first political action committee for psychology. The criteria for engagement in advocacy and the goals and functions of APA’s policy and advocacy initiatives, including the APA Congressional and Executive Branch Science Fellowship Program, are also discussed. The evolution of psychology’s public policy role is illustrated by an increasing level of federal advocacy engagement and effectiveness over time, as well as by the emergence of psychology leaders in Congress and the Executive Branch. The authors’ concluding reflections on the future of psychology in the public policy arena derive from their many years of experience working on or with Capitol Hill, at APA as elected officials or senior staff, and in various roles in academia, think tanks, service delivery, and the private sector.