Background: The ageing of people with intellectual disabilities, with associated morbidity like dementia, calls for new types of care. Person-centred methods may support care staff in providing this, an example being Dementia Care Mapping (DCM). DCM has been shown to be feasible in ID-care. We examined the experiences of ID-professionals in using DCM. Methods: We performed a mixed-methods study, using quantitative data from care staff (N = 136) and qualitative data (focus-groups, individual interviews) from care staff, group home managers and DCM-in-intellectual disabilities mappers (N = 53). Results: DCM provided new insights into the behaviours of clients, enabled professional reflection and gave new knowledge and skills regarding dementia and person-centred care. Appreciation of DCM further increased after the second cycle of application. Conclusion: DCM is perceived as valuable in ID-care. Further assessment is needed of its effectiveness in ID-care with respect to quality of care, staff-client interactions and job performance.