ObjectivesProvision of personalised care planning is a national priority for people with dementia. Research suggests a lack of quality and consistency of care plans and reviews. The PriDem model of care was developed to deliver feasible and acceptable primary care-based postdiagnostic dementia care. We aimed to increase the adoption of personalised care planning for people with dementia, exploring implementation facilitators and barriers.DesignMixed-method feasibility and implementation study.SettingSeven general practices from four primary care networks (PCNs) in the Northeast and Southeast of England.ParticipantsA medical records audit collected data on 179 community-dwelling people with dementia preintervention, and 215 during the intervention year. The qualitative study recruited 26 health and social care professionals, 14 people with dementia and 16 carers linked to participating practices.InterventionClinical dementia leads (CDL) delivered a 12-month, systems-level intervention in participating PCNs, to develop care systems, build staff capacity and capability, and deliver tailored care and support to people with dementia and their carers.Primary and secondary outcome measuresAdoption of personalised care planning was assessed through a preintervention and postintervention audit of medical records. Implementation barriers and facilitators were explored through semistructured qualitative interviews and non-participant observation, analysed using codebook thematic analysis informed by Normalisation Process Theory.ResultsThe proportion of personalised care plans increased from 37.4% (95% CI 30.3% to 44.5%) preintervention to 64.7% (95% CI 58.3% to 71.0%) in the intervention year. Qualitative findings suggest that the flexible nature of the PriDem intervention enabled staff to overcome contextual barriers through harnessing the skills of the wider multidisciplinary team, delivering increasingly holistic care to patients.ConclusionsMeaningful personalised care planning can be achieved through a team-based approach. Although improved guidelines for care planning are required, commissioners should consider the benefits of a CDL-led approach.Trial registration numberISRCTN11677384.