BackgroundAlthough social interaction is important for dementia care and well-being of persons living with dementia, a limited number of studies have reported. This study aimed to examine whether the presence, type, and quality of social interaction is associated with psychological well-being among residents with dementia.MethodsThis study analyzed 258 videos of 30 participants living with dementia. Social interaction was assessed by quality, type, and presence of interaction. Psychological well-being was measured by positive and negative emotional expressions. A mixed model was used for data analysis since these repeatedly measured observation data were nested within subjects.ResultsPositive and neutral interactions were significantly associated with positive emotional expressions after controlling covariates, while negative interaction was significantly associated with negative emotional expressions. There was no significant relationship found between interaction presence or type and emotional expressions.ConclusionsThis study showed interaction quality is essential to promote psychological well-being in persons living with dementia regardless of presence or type of interaction. This study highlights the importance of positive care provider interactions in dementia care. Additionally, institutional efforts to create an environment to reduce negative interactions appears essential to improve the psychological well-being of persons living with dementia.Trial registrationThe study was reviewed and approved by the Yonsei University Institutional Review Board on October 16, 2020 (ref no: Y-2020-0158).