Ecosystem Accounting provides a framework to measure and value relationships between ecosystems, society and the economy. The accounts measure ecosystem extent, condition, and services, providing the means to identify and internalise ecological degradation, as well as understanding the risks and dependencies of economic activities on the environment and tracking progress towards sustainable development. The OSPAR Convention, which concerns the protection of the Marine Environment for the North-East Atlantic, has committed to accounting for natural capital and ecosystem services, where the UN System of Environmental Economic Accounting – Ecosystem Accounting (SEEA EA) provides an international accounting standard for guidance in compiling accounts. Here, we describe the first attempt in compiling accounts aligned with SEEA EA at a Regional Sea scale. We (i) identified existing open access data, (ii) produced accounts for selected ecosystems and valued their services and asset value, and (iii) identified challenges and lessons learned. For ecosystem services, we measured fish provisioning, carbon sequestration, and outdoor recreation from coastal and marine environments across OSPAR contracting parties. The exercise identified lack of fitting data at regional level, spatially explicit linkages and harmonisation need to be overcome to further expand accounts. This work represents an initial step to progress on ecosystem accounting and demonstrates that even with limited data and incomplete timeseries, accounts can start compiling to identify data gaps, and prioritize next steps.