Background: There is an acknowledged urgent need to gather valid epidemiological data in Ireland that provides accurate and reliable estimates of current and future dementia prevalence and facilitates the development of effective dementia health and social policy. This study, commissioned by the Alzheimer Society of Ireland, examined the feasibility of developing a National Dementia Registry for Ireland. Methods: National and international patient registry literature was reviewed to identify registry functions, models, best-practice guidelines, and the legal, ethical, clinical, technology, and financial issues relevant to the creation of a dementia registry in Ireland. Following ethical approval, we conducted two focus groups with people with dementia and twenty-one expert interviews with representatives from Irish and UK research, health, and social care organisations, Irish patient registries and international dementia registries. Discussions followed an agreed structure, were audio-recorded, transcribed and analysed using inductive content analysis. Results: Six themes emerged from these analyses: registry function; registry data; data collection; data management; registry governance and legislation. Three cross-cutting superordinate themes were also identified: benefits and risks, barriers and facilitators, and dementia-specific challenges. Conclusion: These findings provide an evidence-base from which we draw key conclusions and recommend actions to develop a comprehensive National Dementia Registry for Ireland.