There is much policy support internationally for ‘strengths-based approaches’ which work collaboratively with people seeking support. Such approaches aim to recognise the strengths in individuals, those around them, and their communities, to support people to be independent and focus services and support where most needed. However, there is little evidence of how such approaches work in practice or whether they are effective. The Three Conversations (3Cs) is one such approach. Development of practice and future evaluation requires that these approaches are better understood and articulated. To address this challenge, we worked collaboratively with three UK local authorities to understand how 3Cs is operating in practice, and how its evaluation could be considered. We used interviews and workshops with staff, carers and people receiving services, data collected by sites, and wider consultation to develop a theory of change setting out how 3Cs is thought to best operate and be implemented. We identified potential benefits and pitfalls when implementing 3Cs, and barriers to successfully incorporating 3Cs as ‘business as usual’. The theory of change, presented in this article, can be used to support implementation of strengths and relationship-based practice and its meaningful evaluation, and has relevance beyond The Three Conversations.