Unlike environmental non-governmental organisations and other knowledge producers, the European Environment Agency (EEA) seems to attract seemingly little academic interests among scholars of international relations. With this in mind, this thesis seeks to discuss how knowledge institutions such as the EEA may be seen as active participants in IR, while simultaneously seeking to extend academic discussion considering the EEA itself. More explicitly, and in order to narrow down its focus, this thesis is driven by a research question: what is the role of the EEA in policymaking and monitoring done by the European Commission? This thesis adopts social constructivism as its theoretical framework while building on data obtained through both a quantitative content analysis and semi-structured interviews. Both of these methods are used to identify as what kind of a knowledge producer the EEA is institutionalised as a part of the policymaking-complex of the Commission. This thesis finds that the EEA is best understood as an autonomous actor in IR which’s role is to legitimise and support environmental policymaking of the Commission rather than function as an active policymaker itself.