Sustainability education plays a pivotal role in driving change in the present and shaping our global future. This study explores the process of transformative learning among 67 preservice elementary teachers (PSTs) enrolled in a sustainability science course by analyzing six assignments submitted throughout the semester. Using a combined deductive–inductive coding procedure guided by transformative learning theory, our analyses document how PSTs looked inward (e.g., thinking, feeling), outward (e.g., making connections, relating to others), and forward (e.g., taking action) toward building a sustainable future. During the course, all PSTs experienced a disorienting dilemma, the foundation upon which transformative learning takes place. However, few PSTs demonstrated higher-level perspective transformation. When imagining alternative futures, PSTs drew on limited exposure to sustainability-oriented curricula and practices at internship sites, and perhaps as a consequence, most PSTs reflected foremost on their own lifestyles and consumer actions as primary areas for transformation. Moreover, PSTs rarely viewed themselves as potential agents of collective, policy-directed, or collaborative change. Importantly, it was uncommon for PSTs to reflect on their potential role as agents of change as educators who can cultivate sustainability within their classrooms and through their students. Returning to the inward-, outward-, and forward-looking framework, this paper closes with several recommendations for improving the transformative potential of teacher education—particularly towards preparing PSTs to recognize and actualize their potential to influence both what sustainability science content is taught, how these curricula are addressed, and their role in the classroom as agents of societal transformation toward sustainability.