Staff–prisoner relationships have long been recognised as lying ‘at the heart of the whole prison system’ (Home Office, 1984: para. 16; Liebling, 2011). However, relatively few accounts of women's imprisonment have focussed on staff–prisoner relationships specifically, whether describing their terms and dynamics or relating their characteristics to broader ideas of power, trust or legitimacy. In this article, based on semi-ethnographic fieldwork in a women's prison in England, we seek to do something of both, analysing the emotional and relational complexity of staff–prisoner relationships in the context of women's life histories, and the ways that they intersect with flows of penal power and powerlessness. The article illuminates the complexity and emotional intensity of these relationships, first, by outlining their core features, as described by female prisoners – blurred boundaries, infantilisation, pettiness, inconsistency and favouritism – and then by seeking to explain the complex entanglements of power and dependence that result. These explanations include the relative powerlessness and vulnerability of women in prison, their biographical experiences of abuse and trauma, and a tendency for uniformed staff to be somewhat careless in their use of power, while seeking to build close and supportive relationships with prisoners and engaging in forms of benign paternalism. The article concludes that women's prisons represent a challenge to models of penal order, authority and legitimacy precisely because of the relational nature of the flow of power that tends to characterise them.