This chapter develops an analytical framework, drawing on the multidimensional role of integration, to explore how the Ecosystem Approach (EA) is variously conceived and practiced in marine spatial planning (MSP) in the Baltic Sea region (BSR). This framework is used to examine how EA practices reflect differing conceptions of sustainable development (SD) in Baltic marine and coastal areas. This work intersects with several of the other chapters on marine planning in this volume by explicitly exploring links between EA and SD through examination of in-depth BSR case studies. Results reveal that EA principles for MSP developed at the international level (HELCOM/VASAB) and in some national MSP settings (e.g. Latvia), combined with a common assumption of ecological limits to development, largely acknowledge a wide definition of EA as a governance approach building on societal choice and diverse knowledge inclusion (as seen e.g. in the Malawi principles). However, looking at more specific guidelines and MSP practices, there is a significant gap between espoused principles and the practical implementation of EA in BSR MSP, especially regarding social aspects of sustainability such as participation, social inclusion and knowledge pluralism. While work on ecological services in EA looks promising as a means of developing joined-up thinking between ecological and economic interests, it is uncertain whether this approach can deliver on EA’s social sustainability ambitions. We conclude the chapter by discussing ways that could strengthen the social pillar in MSP as a form of governance to bridge the gap between EA principles and practice.