BackgroundDespite consistent recognition of their influence, empirical study of how outer setting factors (e.g., policies, financing, stakeholder relationships) influence public systems’ investment in and adoption of evidence-based treatment (EBT) is limited. This study examined associations among unmodifiable (e.g., demographic, economic, political, structural factors) and modifiable (e.g., allocation of resources, social processes, policies, and regulations) outer setting factors and adoption of behavioral health EBT by US states.MethodsMultilevel models examined relationships between state characteristics, an array of funding and policy variables, and state adoption of behavioral health EBTs for adults and children across years 2002–2012, using data from the National Association for State Mental Health Program Directors Research Institute and other sources.ResultsSeveral unmodifiable state factors, including per capita income, controlling political party, and Medicaid expansion, predicted level of state fiscal investments in EBT. By contrast, modifiable factors, such as interagency collaboration and investment in research centers, were more predictive of state policies supportive of EBT. Interestingly, level of adult EBT adoption was associated with state fiscal supports for EBT, while child EBT adoption was predicted more by supportive policies. State per capita debt and direct state operation of services (versus contracting for services) predicted both child and adult EBT adoption.ConclusionsState-level EBT adoption and associated implementation support is associated with an interpretable array of policy, financing, and oversight factors. Such information expands our knowledge base of the role of the outer setting in implementation and may provide insight into how best to focus efforts to promote EBT for behavioral health disorders.