Introduction: Family carers play an important role in providing care for frail older Australians. Carers have increased rates of depression, burden and poor physical health compared with non-carers. Physical activity has been shown to improve outcomes; however there is limited research investigating outcomes in older carers and less on physical activity for both the carer and care recipient. Research question: Does a home-based individualised physical activity intervention designed for both the carer and care recipient improve depression severity in older carers? Participants and setting: 273 community-dwelling carers with depressive symptoms and their care recipients will be recruited for a randomised controlled trial. Baseline assessment will consist of functional, psychological, and physical measures and information about service use. Intervention and control: Participants will be randomised to receive either a physical activity program (intervention), a social support program (social control), or usual care (control). The intervention and social control groups will have five home visits over six months.