BackgroundThe aim of this study is to 1) explore the experiences of people living with dementia interacting with DFCs and 2) identify factors that influence empower and support people living with dementia to live successfully in DFCs. The main elements of a DFC are related to people; communities; organisations and partnerships. There are over 200 organisations recognised as dementia-friendly in Northern Ireland (NI). This realist evaluation is to understand how DFCs work for people living with dementia, how positive outcomes are achieved, for whom and in what contexts do DFCs work best.MethodsA realist evaluation using case study methodology. The process evaluation includes a realist review of the literature, non-participant observation of people living with dementia in their local communities, semi-structured interviews to explore the facilitators and barriers to living well in DFCs and focus groups comprised of people living with dementia, family caregivers and people working in DFCs to support Context- Mechanisms and Outcomes (CMOs). This four-stage realist assessment cycle is used, including iterative rounds of theory development, data gathering, and theory testing. In the end, analysis will reveal context mechanisms that influence how dementia-friendly communities operate and present an initial theory of how people think, which, if adopted, may be able to alter current contexts so that "key" mechanisms are activated to generate desired outcomes.DiscussionTo give confidence in moving from hypothetical constructions about how DFCs could function to explanations of possible or observable causal mechanisms, the realist evaluation of a complex intervention incorporates a variety of evidence and perspectives. Despite playing a significant role in a person with dementia's everyday life, it appears that little is known about how communities function to achieve intended results. Even though there has been a lot of work to pinpoint the fundamentals and crucial phases of building DFCs, it is still unclear how people living with dementia benefit the most from these communities. This study intends to advance our understanding of how outcomes are produced for people living with dementia by contributing to the underlying theory of DFCs as well as addressing the primary research objectives.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12877-023-04090-y.