Lone mothers are a key target group for government policies to increase employment participation rates. Employment sustainability is central to achieving this goal and thus it is important to understand the factors that affect sustainability. When the lone mother starts work, her daily life changes in various ways, and so do the lives of her children, and perhaps also other family members who may become involved in childcare, or in other forms of help. These social relationships – at home, in work, in care settings, at school – may be a key element in employment sustainability, and one that has not yet been systematically explored in research. This article draws on data from an ongoing longitudinal qualitative study of lone mothers and their children, which has been following the families from the point that the mothers left income support and started working for at least 16 hours per week. The analysis starts from the assumption that sustaining work over time is a process that actively involves the family as a whole and not just the individual lone mother. In this article we explore how social relationships, inside and outside the family, are central to the ‘family–work project’ of sustaining employment.