The achievement of global sustainability and climate objectives rests on their incorporation into policy-making at the level of nation-states. Against this background, governments around the world have created various specialized sustainability institutions-councils, committees, ombudspersons, among others-in order to promote these agendas and their implementation. However, sustainability institutions have remained undertheorized and their impact on policy-making is empirically unclear.In this paper, we develop a conceptual framework for sustainability institutions and systematically explore their potential impact on more sustainable policy-making. We define sustainability institutions as public, trans-departmental and permanent national bodies with an integrated understanding of sustainability that considers socioecological well-being, global contexts and a future-orientation. Drawing on literature on sustainability and long-term governance as well as on illustrative case examples, we propose conducive conditions and pathways through which sustainability institutions may influence policy-making. As conducive, we assume sustainability institutions' embodiment of sustainability governance principles as well as their authority, a strong legal basis, resources, and autonomy. Further, we outline how sustainability institutions can influence policy-making based on their roles in the public policy process. We conclude that the increasing prevalence of national sustainability institutions indicates an ongoing shift from the environmental state toward a more comprehensive sustainability state. However, sustainability institutions can only be one building block of the sustainability state out of many, and their potential to reorient political decision-making effectively toward the socio-ecological transformation hinges upon individual design features such as their mandate, resources and authority, as well as on the specific governance context.