The “Joint Roadmap to Accelerate Marine Spatial Planning Processes Worldwide”, adopted by IOC-UNESCO and the European Commission (DG-MARE) in 2017, highlights the growing commitment of policy and decision-makers in developing transboundary collaboration relevant to Marine Spatial Planning (MSP) as a mechanism for promoting sustainable sea use. While collaboration across borders represents positive progress towards global environmental stewardship and international cooperation, transboundary MSP can present challenges and obstacles as it can be a complex process involving different parties and stakeholders across multiple levels of governance. In this article, we examine the different enabling factors and good practices that emerge from two different DG-MARE-funded knowledge exchange projects on transboundary MSP, whose findings led to the development of the Joint Roadmap: the Baltic SCOPE Project, and the Study on International Best Practices for Cross-Border MSP. Recognising that MSP processes are specific to their respective contexts, we aim to provide guidance and support towards the development of effective collaboration in future transboundary MSP initiatives by offering inspiration in the approaches and tools used elsewhere. We hope this will enable others to reflect on the benefits of adopting a strategic approach to transboundary collaboration designed to align marine plans across different jurisdictions.