Individuals who suffer from severe dementia require assistance when performing activities of daily living. The highly important person transfer situation is influenced by complex, intertwined biopsychosocial factors that are related to the expression of personal, environmental and behavioral variables, which can interfere with the performance of dementia-care dyads' transfer situations. The overall aim of this study was to leverage a behavioral medicine perspective in physiotherapy to explore, intervene in, and develop an assessment scale for problematic person transfer situations including persons with dementia and the interaction with the caregiver in these transfer situations. Interviews were performed with ten caregivers who were recruited to two focus groups and worked in a special care unit for persons with dementia; interviewees described their experiences pursuant to assisting persons with dementia in transfer situations (I). Literature review and video recordings elicited 93 possible items for the new scale. Expert opinions and item-content validity index reduced the number of items to 17 that spanned two areas. Eight items related to the actions of persons with dementias, whereas nine related to caregiver actions. The feasibility testing of the scale in eight person transfer situations showed that the scale was ready for inter- and intra-rated reliability testing (II). Inter- and intra- rater reliability was good (III). In two single-case experimental design studies, the new scale was shown to contribute to a substantial gathering of data on behaviors in care dyads' person transfer situations (IV). In summary, the results of the thesis show that person transfer situations in dementia special care units are influenced by different biopsychosocial factors and that the new assessment scale can support decision-making about treatment strategies. These findings are important in promoting evidence-based behavior change strategies that can facilitate both sets of individuals—i.e., both persons with dementia and caregivers—in transfer situations. The results highlight important research issues that merit attention in future studies.