Introduction Advances in longevity and medicine mean that many more people in the UK survive life-threatening diseases but are instead susceptible to life-limiting diseases such as dementia. Within the next 10 years those affected by dementia in the UK is set to rise to over 1 million, making reliance on family care of people with dementia (PWD) essential. A central challenge is how to improve family carer support to offset the demands made by dementia care which can jeopardise carers’ own health. This review investigates ‘what works to support family carers of PWD’. Methods Rapid realist review of a comprehensive range of databases. Results Five key themes emerged: (1) extending social assets, (2) strengthening key psychological resources, (3) maintaining physical health status, (4) safeguarding quality of life and (5) ensuring timely availability of key external resources. It is hypothesized that these five factors combine and interact to provide critical biopsychosocial and service support that bolsters carer ‘resilience’ and supports the maintenance and sustenance of family care of PWD. Conclusions ‘Resilience-building’ is central to ‘what works to support family carers of PWD’. The resulting model and Programme Theories respond to the burgeoning need for a coherent approach to carer support.