Global climate change poses a significant threat to public health in general and to the health of children, in particular. In response to this threat, many countries have implemented a series of policies to mitigate climate change, among which China's low-carbon city pilot program has attracted widespread attention. This study used longitudinal data drawn from the China Family Panel Studies between 2012 and 2018 to evaluate the impact of China's low-carbon city pilot program on the health of children. A difference-in-differences model was employed to investigate the effects of the policy, with further exploration of potential impact mechanisms. The results demonstrated that China's low-carbon city pilot program substantially improved the health of children by fostering environmental quality and promoting slow mobility (i.e., travel on foot or by bicycle). The study also showed that the impact of the pilot program on the health of children was proportional to their proximity to school. Our findings are significant not only for the expansion of China's pilot policy, but also generally for low- and middle-income countries in their efforts to combat air pollution and understand the scale of its impact on the health of children.