Since 2008, the European Union (EU) increased significantly its involvement in the Arctic and applied to the observer status in the Arctic Council, the most prominent regional forum in the Arctic. Nevertheless, it has made several diplomatic mistakes hampering its actorness in the region whereas the EU holds major strategic interests in the area. As a result, the EU is still perceived by the Arctic States as an external actor, and even as a threat to the current Arctic regime. This study questions the degree of actorness of the EU in the region by analysing its use of scientific cooperation to promote its strategic interests. It analyses the use of science diplomacy by the EU in the framework of the Barents Euro-Arctic Cooperation in relation to the Arctic Council context. This comparison questions the EU’s capabilities and presence by comparison to the Arctic States within the Arctic regional regime. The case study of scientific cooperation allows unveiling diplomatic tools and relays for the EU to potentially increase its actorness by building its legitimacy as a regional actor through the region-building of European Arctic.