Knowledge around urban sustainability interventions is a field of contestation and struggle. This chapter engages with the question of whose knowledge is taken into account in the articulations, implementation and imaginaries of urban sustainability. It specifically examines the justice implications of power asymmetries that are created in the way that certain forms and types of knowledge are valued over others. We examine these dynamics in two ways: (i) the local hierarchies of power knowledge evidenced in cities and in the tensions between vernacular and embodied knowledge versus top-down and disembodied expert knowledge and (ii) the epistemology and different realities that dominant knowledge around urban sustainability represents or erases. Moreover, the knowledge generated by the fields of sustainability and urbanism can be inaccessible to different groups, from policymakers to the public, due to its technical vocabulary and jargon. Lack of translation and brokerage of such knowledge for different audiences creates further inequalities in how urban sustainability can be accessed and contested.