The Mackenzie River Delta is an ecologically rich freshwater environment in Canada’s Northwest Territories. It is vulnerable to multiple stressors such as climate change, resource development activities (oil and natural gas) and upstream-downstream linkages related to extraction activities in the southern part of the Mackenzie River watershed. Resultant socio-ecological impacts affect fishing livelihoods, which represent a significant component of the country food system and ways of life for Inuvialuit (Inuit of the Western Arctic), whose Settlement Area overlaps with the Delta. This thesis analyzes the implications of socio-ecological changes in the Mackenzie River Delta for Inuvialuit fishing livelihoods and the country food system, drawing from Local and Traditional Knowledge. In collaboration with the Fisheries Joint Management Committee in the Inuvialuit Settlement Region, the westernmost Inuit region in Canada, I undertook a participatory-qualitative research, while also drawing on relevant literature and complementary data. Using 28 semi-structured interviews about changes in the Mackenzie River Delta and the importance of fishing livelihoods, results indicated that fishing livelihoods are essential contributors to the Inuvialuit food system, as well as cultural practices surrounding fishing as an activity. Moreover, some results imply the importance of previously ignored species for food security, such as burbot and inconnu, which receive limited attention in other studies. Key findings also indicate that multiple environmental changes are occurring in the Delta, including lower water levels, increasing land erosion, decreasing fish populations, and changes in Delta-reliant wildlife populations (e.g. more beavers), warmer water temperatures, poorer fish quality (e.g. softer flesh, parasites), thinner ice, climate variability, and an escalating cost of living. These changes affect primarily fishing access and raise important concerns about the safety of fish consumption for human health. Ultimately, limited access and declining fish quality have a negative impact on food security, given the key role of fish in the country food system and the importance of socio-cultural dimensions such as fishing knowledge and skills, and sharing practices.