Children's hospitals are unique and inspiring places where, with grit and grace, patients and their families face some of life's toughest challenges. They are places where the state of the art in paediatric care and rigorous research meets the profound human values that children inspire—kindness, hope, and even youthful joy—to help children live longer, healthier lives and overcome diseases that were once incurable. It is now time for children's hospitals to apply their expertise to the next major threat to child health: climate change and the deterioration of the environment.