Sustainability is a concept characterized by its longevity: it remains, after several decades, a popular concept within public organizations, as well as public discourse more generally. In this paper, we trace various translations of sustainability in urban planning documents of three mid-sized cities in Northwest Europe. Emphasizing the importance of a longitudinal approach to assess the uses and definitions of sustainability, we examine translations of the concept across plans through an analytical framework that considers the hierarchical, sequential and integrative linkages between different urban policy documents to understand how local uses of the concept change or remain similar over time. The examination of change and continuity in the translations of sustainability offers insights into how the different manifestations of the concept are influenced by policies external to the city administrations, as well as by imitations of internal, previous policies. This study adds to previous research on contents of plans in relation to how descriptions of concepts take form in a web of interrelated planning and policy documents over time. This paper does so by showing how sustainability as a concept remains on the agenda by being translated into different times and settings, constantly reused with other ideas, and thereby made continuously relevant.