Current reviews of climate-related health threats to children are limited. We performed a systematic review and meta-analysis of studies measuring any child health outcome caused by climate change, with 163 studies eligible for inclusion. We identified many relationships between climate change and child health, the strongest being increasing risk of preterm birth from exposure to temperature extremes. Respiratory disease, mortality, and morbidity, among others, were influenced by climate changes including temperature extremes and air pollution. Children will have increased prevalence of disease due to anthropogenic climate change, and our study is the first to quantify the magnitude of expected increases.