Although the social sciences and planning seem to represent, respectively, the theory and practice of knowledge about cities, neighbourhoods, or regions, their relationship has generally been distant. Increasingly planners and social scientists are working together on research projects and are confronted with different knowledge traditions and methodological understandings of the other discipline. However, social scientists and planners often have different ideas about what research designs and methods are or must offer to fulfil researcher purposes. While social scientists typically focus on theory building and pay particular attention to research rigour such as the validity, reliability and replicability of methods, planners typically focus on research relevance and pay particular attention to solving problems in specific settings using more normative or activating approaches. Often, planners also make pragmatic use of social science methods which disconnects these methods from their knowledge tradition and philosophical foundations. Whereas social scientists actively study and critique methods as part of their discipline, planners often just see methods as a means to an end. These various methodological overlaps, misunderstandings, and conflicts between the social sciences and planning become especially challenging for both social scientists and planners in present-day reality in which research is increasingly expected to be both rigorous and relevant through multi-, inter-, and transdisciplinary modalities. This session focuses specifically on the joint methodological challenges faced by researchers and practitioners worldwide from both the social and planning sciences regarding urban sustainability in the various fields of planning and social-scientific knowledge, including spatial, urban, regional, and transport planning. Contributions may discuss a wide range of methodological challenges in research on involving urban sustainability, including topics such as housing, land use, mobility, just cities or climate injustice. Next to empirical contributions we also welcome methodological reflections about the interaction between planning and social sciences, as well as papers on conflictual experiences in joint projects, or regarding publications, discussions with reviewers, etc.