To examine the association between parental perceptions of out-of-pocket (OOP) health care costs for their child and the total amount of OOP health care expenditures for that child during the past year. We used data from the 2016 and 2017 National Surveys of Children's Health, cross-sectional, parent-reported, and nationally representative surveys of noninstitutionalized US children, ages 0 to 17 years. We conducted bivariate analyses to assess characteristics associated with the amount of OOP expenditures and parental perceptions of these costs. We estimated adjusted prevalence ratios for parental perceptions of OOP costs using logistic regression. Based on parent report, nearly two thirds (65.7%) of children incurred some amount of past-year OOP expenditures, with 13.3% of children incurring expenditures of ≥$1000. Parents reported that costs were unreasonable for 35.3% of children with past-year expenditures. The amount of OOP spending was associated with parents' perceptions that costs were unreasonable, with 16.5% of those with $1 to 249 in expenditures reporting unreasonable costs compared to 77.5% of those with >$5,000 in expenditures (P < .05). In adjusted analyses, high OOP expenditures, non-Hispanic white race/ethnicity, lack of health insurance, low household income, parental education levels less than a college degree, and foreign-born nativity status were associated with reports of unreasonable costs (P < .05). This study demonstrates an association between attitudinal and economic measures of health care expenditures for children while demonstrating differences in the perception of costs by measures of family economic vulnerability. Results may inform efforts to assess adequacy of health insurance coverage. Copyright © 2021. Published by Elsevier Inc.