This dissertation contributes to the vibrant debates on the Geography of Sustainability Transitions in three ways. First, it offers new conceptual perspectives on socio-technical change by bridging approaches from Transition Studies and Economic Geography. The combination helps to shed light on the interplay of drivers, governance processes and changed economic practices. Second, using the ‘forerunner city’ Freiburg (Germany) and the ‘sustainability lagger’ Brisbane (Australia) as case studies, this dissertation provides detailed insights into sustainability transitions in local building and construction sectors – a largely neglected sustainability transition field. Third, it demonstrates how important collaboration and interactive knowledge production between a wide range of actors and stakeholders is to understand processes of change as well as providing knowledge for policy decision-making and guiding industry actors. Drawing on the debates about a ‘geographical turn’ in transition research to better understand socio-economic processes, this dissertation pays special attention to spatio-temporal and relational aspects. Special attention is drawn to the interplay of changed practices, governance processes and the drivers and directions of urban sustainability transitions in these two specific spatial-temporal contexts. The results demonstrate how urban sustainability transitions are contextually specific. Freiburg and Brisbane stand for contrasting pathways based on their specific co-evolutionary dynamics in the building sector, including learning processes, policy support, and involved driving and resisting actors. The Freiburg case study demonstrates how transition pathways were initially driven by a strong grassroots movement from the ‘bottom-up’, then, at a later point, in the interplay of policy-driven ‘top-down’ processes. The Brisbane case study outlines a picture of an ambivalent development. While significant shifts in the commercial building sector can be identified, there is slow momentum in the residential sector. This dissertation is based on a collection of four journal articles. Article 1, “Lost in Transition? Directions for an Economic Geography of Urban Sustainability Transitions”, contributes to the theoretical and conceptual debates on sustainability transitions, and discusses ways of bridging concepts of Economic Geography and Transitions Studies. Article 2, “Interactive knowledge generation in urban green building transitions”, provides methodological insights to the first empirical step of this dissertation – an interactive workshop concept that helped to gain knowledge interactively with a wide range of stakeholders. Article 3, “Sustainability transition pathways in the building sector: Energy-efficient building in Freiburg (Germany)”, offers a detailed analysis of green building transitions in the sustainability forerunner city of Freiburg. The article explains the significant shifts in the local building sector toward increased energy-efficiency. Article 4, “Ambivalent urban sustainability transitions: Insights from Brisbane’s building sector”, sheds light on processes of resistance and challenges in urban sustainability transitions in the building sector.