This article presents a practitioner-based approach to identify key combinations of contextual factors (C) and mechanisms (M) that trigger outcomes (O) in Dutch community-based health-enhancing physical activity (CBHEPA) programs targeting socially vulnerable groups. Data were collected in six programs using semi-structured interviews and focus groups using a timeline technique. Sessions were recorded, anonymized, and transcribed. A realist synthesis protocol was used for data-driven and thematic analysis of CMO configurations. CMO configurations related to community outreach, program sustainability, intersectoral collaboration, and enhancing participants’ active lifestyles. We have refined the CBHEPA program theory by showing that actors’ passion for, and past experiences with, physical activity programs trigger outcomes, alongside their commitment to socially vulnerable target groups. Project discontinuity, limited access to resources, and a trainer’s stand-alone position were negative configurations. The authors conclude that local governance structures appear often to lack adaptive capacity to accommodate multilevel processes to sustain programs.