Housing instability is an important public health issue, particularly for children. This study provides nationally representative estimates of unstable housing among US children. To examine unstable housing prevalence; differences by sociodemographic characteristics, health, and state of residence; and associations with other hardships. This survey study examined data from the 2022 National Survey of Children's Health, a population-based, nationally representative survey of randomly selected children whose parent or caregiver responded to an address-based mail or web-based survey. Participants were children aged 0 to 17 years living in households in the 50 US states and District of Columbia (N = 54 103). Bivariate analyses tested for observed differences in unstable housing between groups; logistic regression models tested for significant disparities. Associations between unstable housing and health care and food-related hardships, neighborhood conditions, and adverse childhood experiences were examined. Unstable housing experiences. Unstable housing, comprising 3 indicators: inability to pay mortgage or rent on time in the past 12 months, 2 or more moves in the past 12 months, and homelessness in the child's lifetime. Analyses were adjusted for child age and family poverty ratio. Secondary analyses examine caregiver-reported stress or worry about eviction, foreclosure, or condemned housing in the past 12 months. Weighted prevalence estimates accounted for probability of selection and nonresponse. In 2022, 17.1% (95% CI, 16.4%-17.8%) of children living in US households, representing more than 12.1 million children, experienced 1 or more forms of unstable housing: 14.1% (95% CI, 13.4%-14.7%) lived in households that were unable to pay mortgage/rent, 2.9% (95% CI, 2.6%-3.3%) moved frequently, and 2.5% (95% CI, 2.2%-2.8%) experienced lifetime homelessness. Additionally, 9.0% (95% CI, 8.5%-9.5%) of children had caregivers who reported stress/worry over housing. Prevalence of unstable housing varied across states (range, 12.0%-26.6%). Unstable housing was highest among American Indian or Alaska Native children (27.9%; 95% CI, 21.3%-35.6%), Black or African American children (30.4%; 95% CI, 27.8%-33.1%), and Native Hawaiian or Pacific Islander children (27.6%; 95% CI, 16.6%-42.1%) and also differed by special health care needs, family poverty ratio, caregiver education and unemployment status, and whether the family rented or owned their home. Unstable housing was associated with all other types of hardships examined. This study found that 1 in 6 US children experienced unstable housing, varying by state and sociodemographic factors. The prevalence is likely underestimated because the sample excluded children who are currently institutionalized or experiencing homelessness. Results may help move the field toward a unified national definition of unstable housing for families with children and lead to clinically appropriate and evidence-based screening and interventions to support housing stability and improve children's health.