Introduction <p>Older adults, particularly those with multiple long-term conditions (MLTCs) and other intersectional characteristics, are under-represented in clinical trials. This includes digitally enabled trials as older people may be less likely to engage with digital methods.</p> <p>We embedded a ‘Study Within a Project’ (SWAP) in TIPTOE, a UK randomised controlled trial evaluating a self-management support intervention for older adults with knee and/or hip osteoarthritis and MLTCs. Osteoarthritis is a musculoskeletal condition that is more common with age. The aim of the SWAP was to understand the barriers to including older people with MLTCs, rapidly develop strategies to support inclusion, and provide methodological guidance for future trials including those that are digitally enabled and/or decentralised.</p> Methods <p>The mixed-methods SWAP spanned three trial phases: (1) set-up, process mapping to establish recruitment pathways and characteristics of local clinical populations; (2) pilot, interviews with recruiting staff to explore attitudes, skills and confidence when recruiting participants from under-served groups; (3) transition to main trial, interviews with participants to explore their experiences of taking part. Rapid analysis enabled changes to be made to trial processes during the early stages of the trial.</p> Results <p>Process mapping identified a diversity of populations and accessibility considerations (e.g. language, unfamiliarity with digital technology). Interviews with recruiting staff (<i>n</i> = 12) identified potential recruitment challenges including concerns that older people may be less inclined to participate due to lower digital literacy or lack of understanding about the trial. Interviews with participants (<i>n</i> = 25) found even those with digital access preferred human support and were concerned about being ‘scammed’ when receiving trial communications. Strategies were introduced such as lowering the eligibility age and creating tailored materials and messaging. Recommendations for future trials include ensuring person-centred support for participants, which has resourcing implications.</p> Conclusion <p>Embedding a SWAP in TIPTOE enabled a greater understanding about recruiting older people who experience intersectional barriers to inclusion. Approaches to support recruitment included providing telephone support for those less confident navigating digital consent and data collection processes and the creation of guidance for sites. The findings could support future trials to better include older people with MLTCs and other under-served groups.</p> Trial registration <p>ISRCTN 16024745. Registered on October 16, 2023.</p>