Given that the majority of frail older people living at home are cared for by family members, ensuring appropriate and sensitive support services for family carers is a major policy priority globally. Such assessment of the needs and situation of individual carers is a crucial first step towards ensuring that they receive flexible, quality support services. However, existing assessment practice is still inadequate in many countries. This paper describes a negotiated approach to carer assessment, the Carers Outcome Agreement Tool (COAT) and briefly considers its development with carers and practitioners in an Anglo-Swedish development project (2003–2005) and subsequent implementation within five municipalities in Sweden (2006–2008). A participatory research design was adopted in both projects building on the ÄldreVäst Sjuhärad model, which is a user-focused approach to research and development. This paper provides a short summary of the COAT development before presenting the qualitative findings from the Swedish implementation project (2006–2008), which emerged from focus group interviews with COAT practitioners and telephone follow-up interviews with carers who had a first and second COAT assessment. The findings clearly highlight the value of COAT in enabling partnerships to be developed between carers and practitioners, which recognise the expertise of both parties. They also challenge providers to invest sufficient time and ‘ear-marked' resources for family care support so that COAT becomes an integral part of a comprehensive long-term carer strategy, which feeds directly into local developments in service delivery and organisation.