Urban planning research is challenged by combining scientific rigour with societal relevance, especially in terms of urban sustainability at local government level. Transdisciplinarity aims to combine rigour with relevance. But how should urban planning researchers, practitioners and other stakeholders collaborate and conduct transdisciplinary research? This chapter reviews the literature on transdisciplinarity for urban sustainability and, instead of advocating specific methods, presents a holistic and flexible methodological framework. The heuristic framework serves to help stakeholders navigate transdisciplinarity and make more considered decisions when conducting transdisciplinary research for urban planning. Practitioner reflections on the framework are provided using the example of Planning Support Science and a customised Planning Support System for climate resilient planning at the local government level in South Africa.