Policy and scholarly efforts to foster sustainable transformations focus on the contribution of practices and institutions; thus far, however, the affects that encourage and enable people to mobilise for and establish these transformative practices and institutions have received less attention. Drawing on the example of the agroecology movement in Brazil, this article examines how affects foster the creation of new farming, community and market relations. It argues that affects play a decisive role in mobilising people and encouraging them to identify and challenge unsustainable relations and practices, develop alternatives, and translate local concerns into policy proposals. It also shows that affects support the establishment of transformative practices by enabling caring relations with nature, and by fostering knowledge and institutional arrangements that support human and non-human others. We conclude that mainstream approaches to sustainability transformations should focus more on building movements of affect, as these not only address sustainability issues but also build and draw on the potential of people to bring about transformation.