Mild frailty is common among older people, but it is potentially reversible with health promotion interventions. Behaviour change may be a key to preventing progression of frailty; however, we know little about what interventions work best and how a behaviour change approach would be perceived by this group. The aim of this study was to explore how mildly frail older people perceive health promotion based on behaviour change and what factors affect engagement with this approach. We conducted semi‐structured interviews with 16 older people with mild frailty who received a pilot home‐based behaviour change health promotion service, including a dyad of older person/family carer, and two service providers delivering the service in two diverse areas of South England. Interviews were audio‐recorded, transcribed and thematically analysed. The concept of goal setting was acceptable to most participants, though the process of goal setting needed time and consideration. Goals on maintaining independence, monitoring of progress and receiving feedback were reported to increase motivation. Physical/mental capability and knowledge/perception of own needs were main determinants of the type of goals chosen by participants as well as the approach used by the project workers. Older people with complex needs benefited from care coordination, with a combination of goal setting and elements of social, practical and emotional support in varying proportions. Mildly frail older people responded well to a behaviour change approach to promote health and well‐being. Further consideration is needed of the most effective strategies based on complexity of needs, and how to overcome barriers among people with cognitive impairment.