Purpose: This qualitative research aims to explore staff perspectives on working effectively with people with intellectual disability who are in contact with the criminal justice system. Design/methodology/approach: Taking a case study approach, staff working for a third sector community organisation were interviewed about the components of effective work with their customers. The staff supported people engaged in the Community Justice Program. Findings: Staff consistently described relationship building as the most important part of their work. There were three components to relationship building: the process of relationship building, the elements of a high-quality staff–customer relationship and the staff skills needed to develop a good relationship. Originality/value: This paper makes two contributions to the literature. First, it focuses our attention on a third sector organisation supporting people in contact with the justice system as opposed to a formal criminal justice agency. Second, the paper seeks to understand the processes and skills staff deploy to build a high-quality relationship with criminal justice-involved people with intellectual disability.