Young people living with disadvantage are at elevated risk of a range of negative life outcomes, including social exclusion, impaired health and well-being, and low educational or vocational participation. In this context, the Resilient Futures program was conceptualized and developed as a strength-focused and positive psychology intervention whose design was underpinned by a broad interdisciplinary range of scientific evidence. The program utilizes an ecological framework that sought to target key proximal and distal factors associated with youth social exclusion, disengagement, and disadvantage. The target participant group was 850 disadvantaged young South Australians (aged 16 to 21) drawn from a number of educational, mental health, and youth justice agencies who were project partners in codesigning and supporting the implementation. The intervention was designed to build well-being and resilience skills through explicit (direct teaching) and implicit (mentoring, case management) teaching methods, supported by system-focused methods that build the capacity of service providers. This article describes the iterative development of the Resilient Futures program, including a significant early program reorientation toward the use of a nonprescriptive and flexible delivery method. This pivot was guided by the implementation science literature, and underpinned by an intentional practice model and approach that was operationalized at both the program design and service delivery layers of the program. We summarize key challenges in delivering a well-being and resilience program across multiple sites for a disadvantaged cohort, and the methods the project team developed to bring focus to implementation quality and rigor. Preliminary qualitative evidence supporting the effectiveness of the program is also provided. (PsycINFO Database Record (c) 2018 APA, all rights reserved)