Scientists and sustainability scholars continue to make urgent calls for rapid societal transformation to sustainability. Science education is a key venue for this transformation. In this manuscript, we argue that by positioning children as critical actors for sustainability in science education contexts, they may begin to reimagine what science means to them and to society. This multi-site, mixed-methods study examined how children’s climate change learning and action influenced their science engagement along cognitive, affective, and behavioral dimensions. For fifteen weeks, ten- to twelve-year-olds participated in an after-school program that combined on-site interactive educational activities (e.g., greenhouse gas tag) with off-site digital photography (i.e., photovoice process), and culminated in youth-led climate action in family and community settings. Participants were 55 children (M = 11.1 years), the majority from groups underrepresented in science (52.7% girls; 43.6% youth of color; 61.8% low-income). Combined survey and focus group analyses showed that, after the program, science became more relevant to children’s lives, and their attitudes towards science (i.e., in school, careers, and in society) improved significantly. Children explained that understanding the scientific and social dimensions of climate change expanded their views of science: Who does it, how, and why—that it is more than scientists inside laboratories. Perhaps most notably, the urgency of climate change solutions made science more interesting and important to children, and many reported greater confidence, participation, and achievement in school science. The vast majority of the children (88.5%) reported that the program helped them to like science more, and following the program, more than half (52.7%) aspired to a STEM career. Lastly, more than a third (37%) reported improved grades in school science, which many attributed to their program participation. Towards strengthening children’s science engagement, the importance of climate change learning and action—particularly place-based, participatory, and action-focused pedagogies—are discussed.