Over the past few decades there have been major successes in creating evidence-based interventions to improve the cognitive, affective, and behavioral health of children. Many of these interventions have been put into practice at the local, state, or national level. To reap what has been learned from such implementation, and to explore how new legislation and policies as well as advances in technology and analytical methods can help drive future implementation, the Institute of Medicine-National Research Council Forum on Promoting Children's Cognitive, Affective, and Behavioral Health held the workshop "Harvesting the Scientific Investment in Prevention Science to Promote Children's Cognitive, Affective, and Behavioral Health" in Washington, DC, on June 16 and 17, 2014. The workshop featured panel discussions of system-level levers and blockages to the broad implementation of interventions with fidelity, focusing on policy, finance, and method science; the role of scientific norms, implementation strategies, and practices in care quality and outcomes at the national, state, and local levels; and new methodological directions. The workshop also featured keynote presentations on the role of economics and policy in scaling interventions for children's behavioral health, and making better use of evidence to design informed and more efficient children's mental health systems. Harvesting the Scientific Investment in Prevention Science to Promote Children's Cognitive, Affective, and Behavioral Health summarizes the presentations and discussion of the workshop.