Background Case management may be a feasible solution to the problem of service fragmentation for people with dementia. Aim To adapt a US model of primary care-based case management for people with dementia and test it in general practice. Design and setting Mixed-methodology case studies of case management implementation in four general practices: one rural, one inner-city, and two urban practices. Practice nurses undertook the case manager role in the rural and inner-city practices, and were allocated one session per week for case management by their practices. A seconded social worker worked full time for the two urban practices. Method Participants were community-dwelling patients with dementia who were living at home with a family carer, and who were not receiving specialist care coordination. Case study methods included analysis of case loads and interviews with patients, carers, local NHS and other stakeholders, and case managers. Measures included numbers of patients with dementia and their carers, number of unmet needs identified, and actions taken to meet needs. Case manager records were compared with findings from interviews with patients and carers, and with other stakeholders. Results The number of eligible patients was smaller than expected. No practice achieved its recruitment target. Researchers identified more unmet needs than case managers. The practice nurse case managers reported lack of time and found research documentation burdensome. Patients and carers were positive about case management as a first point of contact with the practice, as a ‘safety net’, and for creating a one-to-one therapeutic relationship. Conclusion Further investigation is required before case management for people with dementia and their carers can be implemented in primary care.