Many democracies find it difficult to act swiftly on problems such as climate change and biodiversity loss. This is reflected in long-standing debates in research and policy about whether democratic practices are capable of fostering timely, large-scale transformations towards sustainability. Drawing on an integrative review of scholarly literature from 2011 to early 2021 on sustainability transformations and the democracy-environment nexus, this article synthesises existing research on prospects and pitfalls for democratising sustainability transformations. We advance a new typology for understanding various combinations of democratic/authoritarian practices and of transformations towards/away from sustainability. We then explore the role of democratic practices in accelerating or obstructing five key dimensions of sustainability transformations: institutional, social, economic, technological, and epistemic. Across all dimensions we find substantial evidence that democratic practices can foster transformations towards sustainability, and we conclude by outlining a set of associated policy recommendations.