Background Public involvement in research (PIR) can improve research design and recruitment. Less is known about how PIR enhances the experience of participation and enriches the data collection process. In a study to evaluate how UK care homes and primary health‐care services achieve integrated working to promote older people's health, PIR was integrated throughout the research processes. Objectives This paper aims to present one way in which PIR has been integrated into the design and delivery of a multisite research study based in care homes. Design A prospective case study design, with an embedded qualitative evaluation of PIR activity. Setting and participants Data collection was undertaken in six care homes in three sites in England. Six PIR members participated: all had prior personal or work experience in care homes. Data collection Qualitative data collection involved discussion groups, and site‐specific meetings to review experiences of participation, benefits and challenges, and completion of structured fieldwork notes after each care home visit. Results PIR members supported recruitment, resident and staff interviews and participated in data interpretation. Benefits of PIR work were resident engagement that minimized distress and made best use of limited research resources. Challenges concerned communication and scheduling. Researcher support for PIR involvement was resource intensive. Discussion and conclusions Clearly defined roles with identified training and support facilitated involvement in different aspects of the data collection process. This can also ensure that vulnerable older people who participate in research have a positive experience that reinforces the value of their views.