Background Local Healthwatch organisations are an important part of the landscape of health and care commissioning and provision in England. In addition, local Healthwatch organisations are a key means by which users of services are given voice to influence decisions about health and care commissioning and provision. Objective We aimed to explore and enhance the operation and impact of local Healthwatch in ensuring effective patient and public voice in the commissioning and provision of NHS services. Design We used mixed methods, including a national survey (96/150 responses, 68%); actor network theory-inspired ethnographic data collection in five local Healthwatch organisations (made up of 75 days’ fieldwork, 84 semistructured interviews, 114 virtual interviews, observations during the COVID-19 pandemic and documentary analysis) and serial interviews about experiences during the pandemic with 11 Healthwatch staff and four volunteers who were members of a Healthwatch Involvement Panel (which also guided data collection and analysis). Finally, we ran five joint interpretive forums to help make sense of our data. Setting Our five Healthwatch case study organisations are of varying size and organisational form and are located in different parts of England. Results We found significant variation in the organisation and work of Healthwatch organisations nationally, including hosting arrangements, scale of operations, complexity of relationships with health and care bodies, and sources of income beyond core funding. Key points of divergence that were consequential for Healthwatch activities included the degree of autonomy from host organisations and local understandings of accountability to various constituencies. These points of divergence gave rise to very different modes of operation and different priorities for enacting the nationally prescribed responsibilities of Healthwatch organisations locally. Large variations in funding levels created Healthwatch organisations that diverged not just in scale but in focus. As the COVID-19 pandemic unfolded, Healthwatch found new approaches to giving voice to the views of the public and formed effective relationships with other agencies. Recommendations We identified generalisable principles of good practice regarding the collection and communication of evidence. Policy implications relate to (1) the overall funding regime for Healthwatch and potential inequalities in what is available to local populations and (2) the development of Healthwatch’s role given the evolution of local health and care systems since 2012. Future work Future studies should explore (1) the consequences of the development of integrated care systems for local Healthwatch organisations, (2) Healthwatch in an international comparative perspective, (3) how the response to the COVID-19 pandemic has reconfigured the voluntary sector locally and (4) how Healthwatch responds formally and informally to a newly emerging focus on public health and health inequalities. Limitations The survey sought only self-reported information on impact and we were unable to recruit a Healthwatch that hosted several contracts. Conclusions The diversity of the Healthwatch network belies its otherwise unitary appearance. This diversity – especially in differential funding arrangements – has considerable implications for equity of access to influencing health and care planning and provision for residents across England. Funding This project was funded by the National Institute for Health and Care Research (NIHR) Health and Social Care Delivery Research programme and will be published in full in Health and Social Care Delivery Research; Vol. 10, No. 32. See the NIHR Journals Library website for further project information.