Objective: There is powerful evidence that changing people's health-related behavior can impact the leading causes of mortality and morbidity. However, despite the significant potential to improve health and clinical outcomes, behavior change interventions frequently fall short of expected reach or impact. Method: Stakeholder engagement, which refers to the active involvement of public, patients, health professionals, and other decision makers throughout the research process, has been proposed as a strategy to improve the quality, reach, and impact of research. A user-centered "reverse translation" approach makes it more likely that behavior change interventions are relevant to users' needs, better designed, more likely to be implemented, and, ultimately, more effective. Results: In this article, the key concepts of stakeholder engagement are introduced and critically evaluated. Three studies, providing examples of stakeholder engagement, are described and critically evaluated. These include (1) a research prioritization project that sought the views of people with diabetes, services providers, and policy makers to identify research priorities in behavioral diabetes research; (2) a "core outcome set" study, in which consensus methods were used to identify outcomes considered important by patients and health professionals for trials of interventions targeting self-management among young adults with Type 1 diabetes; and (3) an intervention development study, where the intervention targeting self-management among young adults with Type 1 diabetes was coproduced with input from members of a "young adult panel." Conclusions: While stakeholder engagement appears promising as a strategy to increase the impact of behavior change research, evidence is sparse and more guidance, tools, and training are needed.