This article reports on the theory-driven evaluation of a drop-in center for youth that incorporated a literature search, concept mapping with staff, and focus groups with youth. Findings revealed strong agreement among the three sources of data around specific elements identified as critical components of a program theory of global prevention in after-school-hours initiatives, such as drop-in centers. These results are used to illustrate how a theory-driven approach was relevant for the context and objectives of this evaluation, as well as how it was used to develop knowledge useful for action, social intervention theory, and further research.