The Arctic regions are currently undergoing transformative changes linked to globalization and climate change, which pose challenges for current governance structures. This thesis investigates governance in times of change through the lens of reindeer pastoralism, and the traditional ecological knowledge (TEK)- based management in reindeer herding. While studies increasingly highlight the benefits of incorporating TEK into governance, a central challenge remains in finding ways to ensure integration. To contribute such knowledge, this thesis analyses how reindeer-herding local management systems interact with multiple processes of governance steering reindeer pastoralism, and the ways TEK is negotiated in such interactions. Theoretically, the thesis draws on literature on multi-level governance as an analytical framework for engaging with different types of governance processes and actors, and the literature on TEK to conceptualize local social institutions. Methodologically, a qualitative bottom-up methodological strategy (with local reindeer-herding groups and constellations – siidas, brigadas – forming the central starting point for the research) was adopted, focusing on cases from reindeer pastoralism in western Finnmark in northern Norway and Yamal in northwest Siberia. The results show that local reindeer herding organizations are incorporated into processes of governance through participatory, representative and deliberative processes for decision-making. Yet, such incorporation has not facilitated integration of the TEK to processes of governance. A central challenge is that current governance processes are formalized in a way that do not accommodate non-scientific ways of knowing, or non hierarchical consensus-based decision- making. The thesis thus highlights the need for holistic strategies for how to include TEK in governance. Co-management and participatory processes alone are not enough. / IPY EALÁT, the Reindeer Herders Vulnerability Network Study / RUF: Forvaltning i endring