ABSTRACT We propose a type 1 hybrid effectiveness-implementation study to test an adapted evidence-based intervention and explore critical implementation issues, including feasibility, acceptability, and costs, that influence scale-up and sustainment. We focus this adaptation, effectiveness, and implementation study on underserved rural residents, a population that maintains extremely high rates of suboptimal diet and sedentary behaviors, placing them at elevated risk for cardiovascular disease, obesity, diabetes, cancer, and other chronic conditions. Within the vulnerable low socioeconomic status population of rural residents, Appalachian Kentuckians experience even worse health outcomes, including among the highest rates of morbidity and mortality in the nation. Such adversity is exacerbated by and associated with inadequate community resources. Increasingly, however, Appalachian residents and other vulnerable populations are gaining access to modalities that may be useful in addressing these health challenges, including internet connectivity and nearly ubiquitous cell phone use. Despite this accelerating technology use, the evidence base on personal technology-associated interventions (mHealth) in a rural, high need population remains sparse. We propose finalizing adaptation and testing an evidence-based multicomponent mHealth intervention, Make Better Choices 2 (MBC2), a behavioral program consisting of personalized health coaching, an app, accelerometer, and financial incentives. In a recent randomized controlled trial among urban adults, MBC2 produced large, sustained diet and physical activity improvements by leveraging effective behavior change techniques, including goal-setting, self-monitoring, accountability, and support. To prepare for the implementation of this successful intervention with a new population marked by extreme health inequities and sparse resources, our team has engaged in extensive foundational efforts based on the Dynamic Adaptation Process framework. These include: (1) completing focus groups and key informant interviews to assess the feasibility and acceptability for rural Appalachian residents to use the MBC2 program; (2) undertaking a comprehensive community inventory to reveal existing and needed resources; (3) engaging stakeholders in community and academic team meetings, including community forums and CAB meetings; and (4) identifying MBC2 programmatic and structural elements in need of adaptation. With this extensive preliminary activity, we now propose a type 1 hybrid effectiveness-implementation trial in which we: (1) finalize adaptation by wireframe and usability testing MBC2 with local Appalachian residents; (2) conduct a RCT to test the effectiveness of the adapted MBC2 compared to an active control arm; and (3) explore implementation outcomes and contextual factors, with a focus on sustainment. This project aspires to demonstrate that systematic adaptation and implementation of an evidence-based interve...