Urban districts around the world are increasingly developed to be sustainable. In this thesis I explore what comes to count as sustainable in Rosendal, a developing urban district in Uppsala, Sweden. I view Rosendal as an example of contemporary urban sustainability. In light of how urban sustainability initiatives tend to reproduce the status quo, my aim is to question taken-for-granted meanings of sustainability and open up for alternative perspectives. I explore which everyday practices residents of Rosendal associate with sustainability, by drawing upon practice-theoretical approaches. Additionally, I analyse the Sustainability in Rosendal discourse by focusing on the perspectives of Uppsala Municipality and property developers. I approach Rosendal as an urban sociomaterial assemblage, constantly in the process of being made. This perspective helps account for the various practices, discourses and ‘more-than-humans’ shaping what comes to count as sustainable, while decentring humans and bringing forth human interdependency with ‘the environment’. Additionally, the emergent character of assemblages points towards the possibility for urban environments to be developed differently. My findings show that prevailing sustainability meanings reproduced within practices and discourses, do not initiate the type of transformation often called for. Much of what currently comes to count as sustainable in Rosendal is underpinned by a neoliberal growth logic where attractive districts are developed for the chosen few. I show how more-than-human actants, including allotments, cars and wooden panels, contribute to what comes to count as sustainable in Rosendal. By paying attention to the effects of these actants, I envision alternative trajectories for the urban assemblages making up Rosendal. Finally, I suggest that integrating feminist care ethics into urban development can foster more just and transformative sustainabilities.