Background Involving service users in research can be an effective way of improving the practicalities and acceptability of interventions for target end users. Objectives The current paper presented two consensus methods, not commonly used in consultation with service users, to develop a peer support intervention for family carers of people with dementia (SHIELD Carer Supporter Programme). Design Study 1 was a modified Delphi process combined with a consensus conference to explore details of the intervention from the carer and volunteer perspective. Study 2 was an anonymous reader consultation to develop informed consent documents for the intervention trial. Median scores were used to measure and establish consensus. Open‐ended responses were thematically analysed. Setting and participants Study 1: twenty‐five delegates participated (eight were current/former carers) in the first round Delphi questionnaire, with 21 attending the conference. Five completed the Round 2 questionnaire. Study 2: six family carers and 11 people with dementia took part in the consultation. Results Study 1: the role of the peer supporters was developed in terms of relational and practical aspects of the intervention. Study 2: changes were made to the documents, reflecting service user input, but the effectiveness of this less discursive type of service user involvement was unclear. Discussion and conclusions Study 1 methods allowed for service users to contribute significantly and meaningfully, but maybe limiting some design innovation. Study 2 took a more traditional and less collaborative approach. This has implications for balancing the needs of the research with meaningful service user involvement in research.