Within port cities, marine and coastal resources’ exploitation is strongly influenced by interaction patterns existing among the actors living, working and managing such territories. This complexity raises questions about how the physical space can be regulated and how relational configurations between agents can be agreed and formalised. In the port city of Brindisi (Southern Italy), strategic development and planning choices are marked by constant tensions: the community's aspiration to recover from decades of top-down industrialisation face the separation between port and urban planning policies, thus resulting in a conflictual decision-making. Port city planning and policymaking need to be supported by evaluation practices in order to face the complexity both in terms of sustainable port economy, coastal territory uses, and in terms of building a fair, participatory and effective decision-making process. The application of SOCRATES tool, implementing the principles of the Social Multi-Criteria Evaluation (SMCE) methodological framework, allows the identification of the most favourable sustainable development scenario for the Brindisi context, and takes into account the points of view and the possible alliances arising among the different social groups and actors involved. Adopting evaluation as an ex-ante support tool for spatial and maritime planning makes it possible to identify objectives, design site-specific scenarios and select the most preferable alternative. This valuation approach helps to combine a complex and multidimensional strategy, integrating economic, social, environmental and cultural values, and favours the building of shared transformative policies, engaging all actors involved into a participatory decision-making process.