Introduction Mental health service policy stipulates that family carers be involved in care planning. Aim To identify families’ experiences of care planning involvement in adult mental health services. Method An integrative review where electronic databases and grey literature were searched for papers published between 01 January 2005 and 10 February 2016. Results Fifteen papers met the inclusion criteria. Thematic analysis generated three themes: (1) families’ experience of collaboration, (2) families’ perceptions of professionals and (3) families’ impressions of the care planning process. Collaborative decision-making is not regularly experienced by families with an ‘us’ and ‘them’ divide, perpetuated by a lack of communication, confidentiality constraints and a claim of ‘insider knowledge’ of service users. When involved, families perceive care planning to be uncoordinated and that their lived experiences are not always appreciated. Discussion Families need to be valued, empowered and engaged in care planning and the partnership distance be addressed. Accommodating the views of family, service user and professionals is preferable but not always possible. Our findings suggest that the key element for professionals is to value all ‘insider knowledge’ where possible. Implications for Practice Services should develop written information on confidentiality for families and facilitate open communication concerning their involvement in care planning.