This paper theorizes transformative agency and its potential to promote justice-oriented science teacher education. We argue that science education often acts as a disimagination machine, constraining possibilities for envisioning and enacting transformative change. To contest this reality, we draw on critical perspectives in science education, specifically Paulo Freire's and Simone Weil's philosophies to theorize transformative agency as encompassing three dimensions: a) reading the world to identify injustices, b) imagining untested feasibilities, and c) writing the world anew. In doing so, we act upon the belief that inherited practices of science education that negate collective joy must be challenged. We expand current conceptualizations of transformative agency by proposing critical imagination as one of its core components, enabling the envisioning of possibilities for change. We propose three pedagogical approaches for cultivating critical imagination: a) facilitating practices that move beyond the self to recognize multiple human and nonhuman others; b) adopting a planet-centred orientation to education transcending human-centered approaches; and c) troubling dominant spatial and temporal scales of thinking. We argue for the need to develop liberatory pedagogies that bring critical scientific questions to justice issues while nurturing critical imagination. This entails conceiving agency as more than responsive classroom practices but rather as achieving justice-oriented commitments, agendas and visions that center the world and its necessities.