This scoping review is an extended version of a narrative review of couple-centred interventions in dementia shared in part A and the previous publication in this edition. The rationale for expanding study A emerged through the fact that most dyadic interventions have samples consisting of a majority of couples. The exclusion of interventions with samples of mixed relationships in part A therefore contributed to a narrow picture of joint dyadic interventions for couples in which one partner has a dementia. The aim of this second review is to explore the what (types of interventions) and the why (objectives and outcome measures) of dyadic interventions in which sample consists of a majority of couples/spouses and in which people with dementia and caregivers jointly participate. Method A five-step framework for scoping reviews guided the procedure. Searches were performed in Academic Search Premier, CINAHL, PsycINFO, PubMed, Scopus, and Web of Science. Results Twenty-one studies with various types of psychosocial interventions were included. The main outcome measure for people with dementia was related to cognitive function, respectively caregiver burden and depression for caregivers. Conclusions The findings of this extended review of joint dyadic interventions in dementia are in line with the findings of part A regarding the negative approach of outcomes, lack of a genuine dyadic approach, lack of tailored support, neglect of interpersonal issues and the overlook of the views of people with dementia. This review also recognises that measures of caregiver burden, as well as relationship quality should be considered in samples of mixed relationships due to the different significance of burden and relationship quality for a spouse as opposed to an adult child or friend.