The politics, economies, and ecology of the Arctic region are experiencing fundamental transformation driven largely by human-caused environmental change. Drawing on the work of Robert Cox, this article presents a critical account of environmental security that allows security issues in the Arctic to be reconceptualised. It outlines the environmental changes transforming the Arctic, and theorises the Arctic as a regional environmental security complex in which conditions of security for state and non-state referent objects are predicated on a particular ecological context. It then surveys state- and human security issues in the Arctic, and argues that environmental change has destabilised the ecological base on which the contemporary Arctic as a cooperative region supportive of human activity has been built. The article concludes by outlining alternative ways of conceiving of Arctic security that are more compatible with maintaining the region's ecological base, and suggests that dominant approaches to Arctic security are pathological because they remain premised on the control, extraction and consumption of hydrocarbon resources. It argues that, in the context of the geological Anthropocene, security cannot be sustainable if it fails to address the relationship between human wellbeing and human-caused environmental change, or informs practices that further contribute to environmental change.