Background A psychosocial dementia care programme for challenging behaviour (DEMBASE (R)) was developed in collaboration with a Swedish BPSD-registry team for in-home care services use in Japan. The programme consisted of a web-based tool for the continued assessment of challenging behaviours and interdisciplinary discussion meetings. Effectiveness of the adapted programme was verified through a cluster-randomised controlled trial. The Tokyo Metropolitan Government provided municipal funding to introduce the programme into daily practice beginning in April 2018. Objectives To investigate both facilitators and barriers associated with programme implementation. Design A secondary analysis of qualitative and quantitative data. Settings Data were collected in naturalistic long-term care settings from April 2018 to March 2019. Participants A total of 138 professionals and 157 people with dementia participated in the programme. Methods Challenging behaviour in persons with dementia was assessed by professionals using a total Neuropsychiatric Inventory score. Data on expected facilitators and barriers were extracted for qualitative analysis from a debriefing meeting between professionals. Results Of the 157 persons with dementia, 81 (51.6%) received follow-up behavioural evaluations by March 2019. The average level of challenging behaviour was significantly reduced for 81 persons from baseline to their most recent follow-up evaluations. Facilitators included programme available for care managers, visualised feedback on professionals work, affordable for providers and professionals and media coverage. Barriers included professionals from different organisations, unpaid work, operation requirement for municipalities and conflict with daily benefit-oriented framework. Conclusions A follow-up evaluation was not fully achieved. Further strategies to address barriers may include the development of a benefit-rewarding scheme for interdisciplinary discussion meetings, an e-learning system capable of substituting training course portions and a cross-municipality training course.