PurposeThe purpose of this paper is to identify, describe and evaluate the different ways in which formal collective change agency is structured in specialist units inside 25 diverse organisations. As such it is oriented towards a range of practitioners operating in HR, project management or with responsibility for delivering change in public and private sectors.Design/methodology/approachUsing a qualitative design, exploratory interview and case study research was conducted in organisations across the UK public and private sectors to explore how different change agency units operate within organisational structures.FindingsFour dominant types of internal change agency unit are identified, varying in terms of their change impact scope and degree of structural embeddedness in the organisation. These units are described as transformers, enforcers, specialists and independents and share key concerns with securing client credibility and added value, effective relationship management and the use of consulting tools. Their roles and the tensions they experience are outlined along with hybrid forms and dynamic shifts from one type to another.Research limitations/implicationsThe study could be extended outside of the UK and conducted longitudinally to help identify outcomes more precisely in relation to context.Practical implicationsEach of the four types of change agency unit identified is shown to be suited to certain conditions and to present particular challenges for collective change agency and for specialist management occupations engaged in such work. The analysis could usefully inform organisation design decisions around internal change agency.Originality/valueThe authors extend debates around the nature of internal change agency which has typically focussed on comparisons with external change agents at the level of the individual. Developing the work of Caldwell (2003), the authors reveal how emergent, team-based or collective approaches to change agency can be formalised, rather than informal, and that structural considerations of change need to be considered along with traditional concerns with change management.