Nowadays, cities formulate long term strategies to address the challenges and opportunities they face. Numerous strategic plans or planning instruments are developed to this purpose. In this article we want to examine the role, impact and relevance of these types of plans in decision-making processes concerning urban development projects (UDPs) in the Flemish Region of Belgium. To what extent do strategic plans succeed in capturing and steering the complexity of spatial interventions in contemporary urban contexts? We argue that a complexity acknowledging perspective provides a more realistic and adequate view here by seeing strategic plans as only one among many elements in the set of tangled inter- and intrastrategic processes which together determine UDPs. A comparative and qualitative case study was carried out in the city of Kortrijk. The decision-making of three UDP’s was studied thoroughly. Interviewing key actors and analysing policy documents helped us to (re)construct the complex decision-making processes and to stipulate the meaning of all involved formal plans and planning tools.