The aim of this project platform is to build on the outcomes of existing and previous projects to establish a regional framework for integrating Strategic Environmental Assessment (SEA) within Maritime Spatial Planning (MSP) across the Baltic Sea region. More specifically, the project platform aims to strengthen the role of MSP in promoting sustainable blue economy and enhancing the management of human activities at sea, as a key element of ecosystem-based approach. As a significant component of the SEA, the platform also aims to develop methodological recommendations for cumulative impact assessment (CIA) in transboundary context as core element of SEA in MSP. By synthesizing and validating prior SEA and CIA practices and recommendations, this platform will refine practical tools and guidelines to address transboundary challenges such as climate change, renewable energy expansion, and biodiversity conservation. Through collaborative workshops, capacity-building initiatives, and pilot applications, the project platform will leverage validated methodologies, ensure the long-term adoption of SEA and CIA, and enhance interoperability between assessment tools. Ultimately, this platform will enable more sustainable, resilient, and collaborative MSP processes across the region.