Supportive social interactions between nonparental adults (i.e. social work professionals, volunteers, and other parents that have contact with children but are not the primary caregiver), parents, and children are important for children's well-being and development. Parenting styles, types of child behaviour, and location in the neighbourhood may influence these interactions. The aim of the present study was to identify when and how nonparental adults respond in interactions with other adults and children in the neighbourhood. A mixed-method study with vignettes and interviews (N = 114) was conducted to gain insight into which factors (parenting style, child behaviour, location in the neighbourhood) influence the nonparental adults' intention to respond to children and/or parents. Nonparental adults indicated they were most likely to respond in the context of a permissive parenting style or a child's externalising behaviour. Professionals more often felt responsible than parents and volunteers, although they did not respond more often. All three factors were related to the participants' willingness to respond and promote a supportive social structure in the neighbourhood. Social work professionals and their organisations can use this study to identify social support interactions and to discuss their responsibilities.