The implementation of an ecosystem-based approach (EBA) is a core requirement of the EU Maritime Spatial Planning (MSP) directive. Ecosystem-based management presents a fundamental challenge to established practices concerning the planning of marine space and the governance of human activities at sea. Experience to date indicates considerable variation in the application of EBA across Europe. This variation can be attributed in part to differences in underlying planning traditions and cultures. In this article, we examine the specific case of EBA implementation in the current maritime spatial plan for Germany’s Exclusive Economic Zone (EEZ). Following an interpretive analysis approach, we critically analyse how the scope and function of planning are understood in German MSP policy and practice. A narrow understanding of planning as solely concerned with the spatial coordination of competing claims on marine space is traced to a legalistic terrestrial planning tradition with a long history in German public administration. This narrow interpretation of the role of planning is found to fundamentally restrict the strategic, performative capacity of German MSP and, in particular, the potential for German MSP to apply ecosystem-based management principles. In conclusion, we contend that the implementation of an EBA requires a fundamental shift in planning paradigms and modes of governance. This empirical case provides a basis for critical reflection on the capacity of EU member states to implement an EBA as understood under the MSP directive and the mode of planning this might entail.