Purpose Supported decision-making (SDM) is an emerging and innovative alternative to substitute decision-making practices. While relationships are pivotal in establishing proper and effective SDM, scant research has examined these relationships in-depth. This study explores how decision-making supporters perceive relationships embedded in SDM for adults with disabilities. Furthermore, it compares the points of view of family and volunteer supporters on these relationships. Materials and methods Using a semi-structured interview guide, in-depth interviews were held with 16 family and 16 volunteer supporters of Israeli decision-makers with disabilities. Results Both family and volunteer supporters addressed the centrality of the support relationship. However, they differed in their perspectives on the ways such relationships should be formed and on their boundaries. We distinguish between families’ continuing relationships vs. volunteers’ emerging relationships to emphasize the identified differences. Conclusions The findings highlighted the importance of relationships to SDM processes, highlighting the need to examine in greater depth whether and how “typical” family relationships differ from SDM relationships. Based on these findings, we recommend training and guidance for both family and volunteer supporters in developing and strengthening these relationships.