The impact of COVID-19 public health interventions on pediatric illnesses nationwide is unknown. We performed a multicenter, cross-sectional study of encounters at 44 children's hospitals in the United States to assess changes in healthcare utilization during the pandemic. The COVID-19 pandemic was associated with substantial reductions in encounters for respiratory diseases; these large reductions were consistent across illness subgroups. Although encounters for nonrespiratory diseases decreased as well, reductions were more modest and varied by age. Encounters for respiratory diseases among adolescents declined to a lesser degree and returned to previous levels faster compared with those of younger children. Further study is needed to determine the contributions of decreased illness and changes in care-seeking behavior to this observed reduction.