This report assessed the extent to which biodiversity is mainstreamed across EU, regional, and national marine and sectoral policies, with a particular focus on the role of the Maritime Spatial Planning (MSP) Directive. The analysis shows that while biodiversity conservation is well embedded in environmental policies and increasingly acknowledged across sectoral frameworks, its practical integration and implementation remain uneven across countries and policy domains. Despite strong policy recognition of MSP as a key tool for biodiversity protection, its potential is not fully realised in practice, due to institutional, technical, and resource-related barriers. The findings highlight the need for stronger mechanisms to connect MSP processes with concrete biodiversity actions, as well as for enhanced coordination through frameworks such as Regional Sea Conventions to support more effective and coherent implementation.