Safety-net programs improve health for low-income children over the short and long term. In September 2018 the Trump administration announced its intention to change the guidance on how to identify a potential "public charge," defined as a noncitizen primarily dependent on the government for subsistence. After this change, immigrants' applications for permanent residence could be denied for using a broader range of safety-net programs. We investigated whether the announced public charge rule affected the share of children enrolled in Medicaid, the Supplemental Nutrition Assistance Program, and the Special Supplemental Nutrition Program for Women, Infants, and Children, using county-level data. Results show that a 1-percentage-point increase in a county's noncitizen share was associated with a 0.1-percentage-point reduction in child Medicaid use. Applied nationwide, this implies a decline in coverage of 260,000 children. The public charge rule was adopted in February 2020, just before the coronavirus disease 2019 (COVID-19) pandemic began in the US. These results suggest that the Trump administration's public charge announcement could have led to many thousands of eligible, low-income children failing to receive safety-net support during a severe health and economic crisis.