Physical inactivity in older adults presents a significant problem within contemporary society. Governments around the world are recognising this importance and the large impact of physical inactivity on health and health-related expenditure, yet interventions promoting physical activity have typically produced only small or short‐lived behaviour change. Through three related studies, this thesis aims to develop a person-centred, multi-level physical activity intervention within a residential estate of older adults. The first study used qualitative methods to develop a person-centred understanding of the multi-level influencers of physical activity engagement within the targeted individuals. These findings were then applied within study 2, which implemented a 12-week physical activity intervention within the residential estate and used a mixed-methods approach to assess its implementation and explore personal experiences of the intervention strategies designed by the person-centred approach. The final study explored the transitions associated with older adults to develop an understanding of purpose, meaning and identity in later life, and how this can influence physical activity behaviour. The findings of the third study were presented within a composite vignette of the transition experiences of 4 older adults within the residential estate. The thesis presents an effective and appropriate strategy for developing person-centred, multi-level physical activity intervention for older adults. Contrary to the health-focused emphasis that is predominantly adopted by public health initiatives, the findings of this thesis highlight the importance of purpose, and related constructs such as meaning and identity for understanding and promoting physical activity behaviour in older adults. The findings suggest that future person-centred physical activity interventions for older adults should take into consideration the changes in sense of purpose as individuals become older and design intervention strategies to maximise a sense of purpose in life, and to provide more meaningful sources of physical activity.