‘This paper reports on findings from a qualitative study of practitioner–service user relationships in social work. The research aimed to identify social workers’ personal constructs of their relationships with service users and explore how these constructs differed across roles and settings. A qualitative methodology employing a variation on role repertory grid techniques was used to carry out semi-structured interviews with social workers. Twenty-five social workers from seven different practice settings were interviewed and altogether identified over 200 personal constructs. The research team undertook a thematic analysis of these constructs along with their explanation and discussion in interview transcripts. The results identified twenty-five superordinate constructs within ten core themes, which reflected practitioners’ experience of relationships, their systemic context, along with dynamics of power and collaboration. The constructs were often found to contrast a positive or preferred attribute of relationships with a more negative or challenging attribute, although the reality of relationships was often found to be complex and ambiguous. Some implications are explored for current theories of relationship-based practice in social work.