The involvement of service users (people who use health and social care services) in research is central to UK policies, is an integral component of many research funding programs and improves the quality and uptake of research. People with intellectual disability are often excluded from research involvement. The purpose of this article is to describe how adult service users with intellectual disability were involved in the early stages of a diabetes screening study conducted in Leicestershire, UK. People who volunteered were involved in five key areas: publicity, study documentation and process development, acceptability of measures, recruitment of research staff, and training of staff. Service users helped with logo selection, publicity materials, designing art work, raising awareness of the study, study documents, rehearsing clinics, and recruiting and training research staff. Our findings demonstrate that with careful planning adults with intellectual disability can meaningfully be involved and benefit from involvement in research. We look forward to continued involvement with service users with intellectual disability in future research studies.