Background <p>Frailty is a multidimensional condition that increases vulnerability to poor health outcomes, yet older adults living with frailty are often underrepresented in research or involved only in limited ways. Engaging people with lived experience can improve the relevance, acceptability, and impact of research, but little is known about the involvement of older adults living with frailty across the research process. This scoping review explored how engagement is practiced, the roles older adults play at different stages of research, and the effectiveness of these approaches.</p> Method <p>The review followed the methodological guidelines of the Joanna Briggs Institute. Five databases and Google Scholar were searched for articles published in English between 2005 and 2025. Eligible studies included those that described when and how older adults living with frailty were involved in the research process. Two reviewers independently screened titles, abstracts, and full texts to select articles and extracted data using a structured template. Data were analyzed to categorize engagement approaches, assess levels of engagement across research stages, and evaluate the effectiveness of these approaches.</p> Results <p>Ten studies met the inclusion criteria. Most used participatory and action-oriented, co-design and human-centred design, patient and public involvement and priority-setting, or dialogic and capacity-building approaches. Engagement was strongest during the early stages of research. Older adults living with frailty frequently contributed to identifying priorities, shaping study aims, refining tools and interventions, and participating in collaborative workshops. Across studies, involvement was described as meaningful and personally empowering, contributing to increased confidence, social connection, and a sense of being valued. Engagement also produced tangible research outcomes. However, involvement declined substantially in later stages. Only a few studies engaged older adults in interpreting data, reviewing results, co-presenting findings, and contributing to implementation efforts, and no study provided shared decision-making authority across the full research cycle.</p> Conclusion <p>This review shows that engaging older adults living with frailty in the research process is both feasible and valuable. To advance the field, future work must extend engagement beyond early stages by fostering continuity, transparency, and shared decision-making through flexible practices and explicit attention to power and governance.</p>