Large-scale urban regeneration projects become highly complex as they involve multiple actors with different expectations. In general, the implementation of such projects entails building governance regimes at the city or regional level, but this often means forging partnerships between public and private actors to serve as policy instruments. Each city government formulates its own strategy for coping with the complexities of various levels of policy-making, thereby establishing multi-level governance regimes. And each city has its own particular experience with the implementation trajectory: long or short, successful or unsuccessful. This paper focuses on how the complexities of multi-actor governance influence the implementation of these projects. The purpose is to show how the macro-level institutional context affects the project’s success and to analyse the challenges posed by multi-actor governance. Comparative analysis of two old port regeneration projects, namely Rotterdam’s Kop van Zuid in the Netherlands, and Het Eilandje in Antwerp, Belgium, reveals how similar challenges were dealt with in different institutional contexts.