Following Affordable Care Act (ACA) implementation in 2014, children’s and parents’ insurance coverage and Medicaid/Children’s Health Insurance Program (CHIP) participation rose, and the number of Medicaid/CHIP-eligible uninsured children and parents fell. But between 2016 and 2017, children’s coverage and participation decreased, and parents’ gains stalled. Uninsurance rose between 2016 and 2017 among both children and parents in nonexpansion states, and both groups remained more likely to be uninsured in nonexpansion states than expansion states. As in prior years, we found that parents were over twice as likely as children to be uninsured in 2017 and found notable variation across states and subgroups.