Aim: It is unclear whether carer‐held records (CHR) are useful for patients with dementia. In this study, we evaluated the usefulness of the CHR for patients with dementia at the municipal level. Methods: Candidates for CHR use in this study were informal caregivers of patients with dementia who lived at home in Kawanishi, Japan. CHR users were those who are involved in the patient's care and treatment, such as informal caregivers, family physicians, dementia specialists, care professionals, and care service coordinators, known as ‛care managersʼ in Japan. Collaborative meetings were held every month mainly to help users, especially care managers, learn how to effectively use CHR. We surveyed informal caregivers before and 1.5 years after the start of CHR use to evaluate whether CHR improved collaboration and information provision. The Zarit Caregiver Burden Interview and Dementia Behaviour Disturbance Scale were also administered. We divided the informal caregivers who continued CHR use for 1.5 years into two subgroups based on whether their care manager attended the collaborative meetings at least twice. In addition, we divided informal caregivers into three subgroups depending on their relationship to the patient: spouse, child, or daughter‐in‐law. Results: The study initially consisted of 201 informal caregivers. Among them, 74 informal caregivers continued CHR use for 1.5 years. The information provision score significantly improved after CHR use for all informal caregivers. The collaboration score significantly improved after CHR use only for informal caregivers whose care managers attended at least two collaborative meetings. The Zarit Caregiver Burden Interview score significantly improved after CHR use for daughter‐in‐law caregivers. The Dementia Behaviour Disturbance Scale scores did not significantly improve after CHR use. Conclusions: CHR were useful for informal caregivers of patients with dementia. However, care managers need to teach informal caregivers how to properly use CHR.