Public policy is increasingly made and governed using experts across many levels of ‘governance’ – from the international to the local. But how experts influence the design of this ‘multi-level’ governance is not well understood. This thesis investigates this puzzle by examining how groups of experts, conceptualised as ‘epistemic communities’, and those processes of multi-level governance influence each other. But the design of those processes can also be influenced by matters such as national identity. Therefore, the thesis also explores the extent to which experts holding a linguistic cultural identity, which highlights the importance of language and associated culture, influences the epistemic community-multi-level governance relationship. This study uses a specific definition of expertise to describe epistemic communities, which concerns the mastery of the language and practice of a field of knowledge, to make an original contribution to the literature. A further important contribution is made by examining the relationship between epistemic communities and multi-level governance in new settings. The cases of the development of the Loi sur le patrimoine culturel and the Historic Environment (Wales) Act in Québec and Wales show the usefulness of cultural heritage policy in these territories for understanding the two concepts. Epistemic communities were found to ‘frame’ policy problems, especially those that were technical or uncertain, in ways that created demands for more expertise. The design of multi-level policymaking processes was shown to be frequently shaped by these frames to different extents. Linguistic cultural identity shaped epistemic community actions too, at times, especially when it was perceived as politically relevant. This influenced multi-level policymaking designs primarily by reducing the number of different actors and different fields of knowledge represented. The findings imply that experts can be very important for shaping the design of policymaking processes but that this may limit their effectiveness and legitimacy.