Climate change is an urgent global environmental crisis that requires widespread action and an educated, motivated citizenry. This study explored the impacts of a Climate Superheroes STEAM camp on preschool children's ideas about climate-friendly actions. The research employed a mixed methods experimental design approach including a quantitative pre/post-test, qualitative activity prompts, field notes, and a post-camp parent survey. The sample included 27 children aged 3 to 6 years and 11 of their parents. Preschool children made significant gains on their understanding of climate-friendly actions, using reusable materials, turning off lights when not in use, and gardening. Children demonstrated many correct ideas about how and why climate-friendly actions helped the Earth and some common misconceptions as well. Children gained knowledge of accessible climate actions, and qualitative results show some increase in agency for taking climate action. Implications for early childhood education and environmental education related to climate change are explored.