Background: Adults with intellectual and/or developmental disabilities are disproportionately excluded from participation in research, consequently increasing disparities experienced by this group. Gatekeepers, individuals who control access to research participation opportunities, may either support or pose a barrier to inclusion in research. We sought to understand how gatekeepers serve as supports and barriers to the participation of people with intellectual and/or developmental disabilities in research and the factors that may drive their actions. We also sought to identify approaches to interacting with gatekeepers that promoted the sharing of research participation opportunities.Methods: We conducted a scoping review of manuscripts published between January 2009 and September 2024 describing gatekeeping during recruitment for adults with intellectual and/or developmental disabilities in social/behavioural research. We conducted content analysis of 22 manuscripts to identify ‘gate opening’ actions (actions that support research participation) and ‘gate closing’ actions (actions that pose a barrier to research participation) at the point of recruitment. We also identified approaches researchers took when interacting with gatekeepers to promote gate opening actions.Results: Gatekeepers' attitudes (e.g., valuing research) and knowledge about prospective participants were associated with gate opening actions. Gatekeepers' attitudes of mistrust of researchers and/or research, deprioritisation of research and presumed incapacity of people with intellectual and/or developmental disabilities to consent to, participate in and/or benefit from research participation were associated with gate closing actions. Gatekeepers' lack of information (e.g., about research and prospective participants) was also associated with gate closing actions. Restrictive organisational policies and gatekeepers' lack of resources (e.g., time) were also associated with gate closing actions. Approaches for interacting with gatekeepers that may foster gate opening actions included: addressing gatekeeper concerns, educating gatekeepers about the benefits of research participation and developing relationships with gatekeepers.Conclusion: We identified several malleable factors that may drive gate opening and gate closing actions. Enhanced collaboration between researchers and gatekeepers may foster greater opportunities for individuals with intellectual and/or developmental disabilities to learn about research opportunities.