In the urban context the quest to enhance economic growth and social well-being is challenged by the need to protect and manage natural resources. In order to promote sustainable urban planning, sustainability objectives are commonly embedded into planning policies, and the associated indicators used to evaluate planning interventions and monitor implementation of such objectives. The applicability of indicators is commonly tied in to their ability to address context-specific issues and monitor progress towards definite goals set at the local level. This paper presents the findings of a participative methodology applied in five European cities to develop a set of sustainability indicators with the aim of optimising their applicability for assessing planning alternatives affecting urban metabolism (i.e. the exchange of materials and energy within cities). The results indicate that engagement of researchers and practitioners through Communities of Practice (CoP) helped bridge the gap between science and practice, and facilitated the selection of consistent and meaningful indicators to be used as a tool for decision-making. However, the results also revealed that planning priorities can significantly shape the extent and scope of sustainability indicators, and that a CoP approach may not always be sufficient to guarantee continuity of collaboration.