This article presents a synthesis of two PhD studies of Support Family Intervention (SFI) in Finland. This is a service in which volunteer families provide support and respite care to children and parents who are coping with a range of psycho-social challenges by looking after the children for one weekend a month. The aim of this article is to develop a child-centred programme theory (CCPT) of SFI that combines a meta-ethnography-based theory underpinning the use of SFI with evidence of participating children’s lived experiences. The CCPT that emerged is grounded on three elaborations of the programme theory currently informing SFI: a more nuanced description of the child as a stakeholder in the intervention, an investigation into the supportive properties of the environment and the activities provided by the support family to the child and clarification of the function of relationships as a central element of the intervention.