Background: This article describes the process of including people with intellectual disabilities (ID) and carers of people with ID as researchers and participants in randomised controlled trial (RCT) research. People with ID are rarely involved in research about their health, either as researchers or participants. Carers are often included as research informants, but family carers are rarely involved as researchers. Method: Four teams of researchers each comprising a researcher with ID, a supporting professional and a carer researcher, were recruited to complete a health intervention RCT. Accessible measures were selected and/or devised. Baseline interviews were completed by researchers with ID and/or carers of people with ID by asking participants with ID and/or carers of the participant about the health of the person with ID. Follow-up health interviews were administered after the intervention had been in place for a year. Results: The researchers completed 331 interviews with carers and 196 with participants with ID. Over 50% of participants with ID completed baseline assessments. Positive feedback on the process and outcomes was given by the researchers involved. Conclusion: The inclusion of people with ID both as researchers and as participants was achieved through an appropriate design, strong research partnerships, adequate and flexible resources, promotion of teamwork and a strong task focus.