Background: The implementation of evidence-based programmes (EBPs) designed to improve outcomes for children and young people and prevent disadvantage is an increasingly important international policy imperative. However, the integration of EBPs into existing service settings and systems is a complex and multifaceted undertaking. Methods: A process evaluation was conducted to appraise the design and development of a large-scale, areabased, prevention and early intervention initiative. This initiative, called Youngballymun, consisted of five service strategies comprising a range of EBPs (e.g. the Incredible Years Programme, Highscope) targeted at children and young people and their families (from birth to 20 years). The initiative was designed to promote the development, adoption and implementation of EBPs within routine children and youth services in a disadvantaged urban area in the Republic of Ireland. The analytical approach involved the systematic analysis and triangulation of data obtained from relevant documentation (e.g. programme manuals, meeting minutes), as well as a series of one-to-one interviews (n = 27) and six group discussions with key stakeholders (n = 29). Results: Adopting aspects of an implementation stages framework (Fixsen, Naoom, Blase, & Friedman, 2005), we examined the key implementation stages of exploration and installation. Data gathering and needs assessment and strategic organisational development played an important role in implementation. However, resistance to innovation amongst local service providers emerged as a major challenge to implementation. Factors identified as crucial to overcoming this challenge and promoting stakeholder buy-in for innovation included: encouraging and supporting stakeholder engagement; and adopting a flexible approach to implementation planning. Conclusion: Generating buy-in amongst stakeholders is central to ensuring a fit between innovative programmes and practices and the systems in which they are to be embedded. Some key lessons, such as the need for the active involvement of community-based service providers in the planning process at the earliest stages of implementation, are identified. The kinds of implementation strategies that may be used to address challenges to practice change and innovation, particularly stakeholder responsiveness to, and perceived compatibility of, EBPs, are discussed.