Behavioral science is the study of how people make choices and act upon them. Instead of assuming people are perfectly rational and always make decisions in their best interests, the field uses lessons from psychological research that show that most people are susceptible to personal biases, logical fallacies, and heuristics. The private sector has long relied on behavioral science insights to develop effective business practices and refine service delivery. Increasingly, researchers and policymakers are applying lessons from the field to government programs and policies. Behavioral science insights can be used to increase uptake of available services and to design programs and policies to help consumers better navigate complex decisions. Using behavioral science techniques to develop and test interventions can be a cost-effective way to improve outcomes and promote evidence building through testing and data analysis. This brief describes the use of behavioral science in the public sector and its role in promoting evidence-based policymaking.