Water is a fundamental component of the ecological integrity, economic development, and sustainability of northern regions, as well as the health and well-being of northerners. However, environmental change has altered fragile thermodynamic relationships of northern ecosystems by shifting seasonal transitions, altering precipitation regimes, reducing snow and ice cover, and increasing exposure to solar radiation. This has exacerbated existing pressures on freshwater supply that have arisen from increased resource development, inappropriate or inadequate infrastructure, population stress, erosion of Indigenous knowledge systems and culture, and inadequate policy and management. Since water governance systems in northern Canada are under rapid evolution, we examine key vulnerabilities to both the quantity of accessible freshwater and the quality of available freshwater resources for communities in Nunavut, Arctic Canada, within a water security framework. While the concept of water security is often approached from a human-centred perspective, we note the importance of integrating a biophysical perspective. We also compare information and experiences of the other northern regions to assess how water security is conceptualized and addressed across northern Canada, identifying biophysical and social vulnerabilities as well as implications for governance and adaptation.