This study assessed differences between service users’, family carers’ and mental healthcare providers’ perceptions on service user and family carer involvement in mental healthcare. We conducted questionnaires in care networks for persons with serious and persistent mental illness, among 111 service users, 73 family carers and 216 mental healthcare providers. Many aspects of service user and family carer involvement are achieved to satisfactory levels while other aspects are scarcely realized. Service users and mental healthcare providers perceive family carer involvement as less important and realized than service user involvement. Family carers hold more favorable views on the importance and realization of involvement than do mental healthcare providers. The implementation of stakeholders’ involvement in healthcare is ongoing. Notwithstanding great efforts, service users’ and family carers’ involvement preferences are not yet fully considered. Developing procedures, training and monitoring cycles regarding involvement may enhance this situation.