Objectives: The aim of this study is to explore the extent to which staff-resident interactions address or undermine residents psychological needs and how such interactions are associated with residents well-being. Method: Data on staff-resident interactions and residents well-being were collected for 51 residents from nine long-term care settings using dementia care mapping (DCM). DCM yields a count and detailed description of staff-resident interactions that either address (personal enhancers - PEs) or undermine (personal detractions - PDs) residents psychological needs, and every 5-minute scores for each resident's mood and engagement (ME-value). The relationship between PEs and PDs and well-being was analysed by studying residents ME-values before and three time frames after a PE or PD occurred. Results: A total of 76 PEs and 33 PDs were observed. The most common PEs were those addressing psychological needs for comfort and occupation. However residents well-being increased most often after PEs that addressed residents need for identity, attachment and inclusion. The most common PDs were those which undermined the need for comfort, inclusion and occupation. Residents well-being decreased most often after PDs that undermined the need for comfort. Conclusion: Increasing interactions which address residents need for attachment, identity and inclusion and eliminating interactions which undermine residents need for comfort may be particularly important in achieving residents well-being. In the long run, residents well-being could be achieved by staff availing of the opportunities to empower and facilitate residents, thus meeting their needs for occupation. These findings provide directions for training in person-centred care.