Aim: The present study aimed to explore the impact that changes in behavioural symptoms of people living with dementia have on professional caregiver and resident relationships. Method: A total of 21 interviews were carried out with professional caregivers of people living with dementia. A grounded theory approach was used to investigate everyday experiences of provision of professional care in dementia settings, focussing specifically on the effect of behavioural change on such relationships. Results: A core category emerged from this analysis: 'Developing behaviour in dementia impacts relationships on a personal and professional level'. Discussion: Professionals have recognized as part of their everyday practice an eventual deterioration in relationships between themselves as professional caregivers and the residents, but also between the residents and their family members and among residents themselves. Importantly, understanding patients' behaviour and behavioural change was identified as a crucial factor to achieve and sustain good relationships between professionals and residents suffering with dementia.