Agency among young women is often understood as fleeting in nature, and studies rarely offer insights into how agency could become a more sustained position. Using data from 54 young women discussing their sexual and intimate relationships, this paper suggests a new way of understanding agency beyond that found in work which stresses agentic practice as resistance or the challenging of dominant expectations and understandings. Instead, through the notion of 'agency in action' we begin with young women's conceptualisations of power. In this study, power was viewed as a resource that is shared between partners, but also a capacity of the self. These conceptualisations offer two new ways of understanding agency in intimate relations - either through 'reacting into action' and taking power back; or by 'starting from' a powerful position. Central to an understanding of young women's agency is the role of emotions and recognition of these as motivators for change.