Research has documented several collateral consequences of parental incarceration for the development of children. However, there is limited research on how experiencing parental incarceration impacts the school readiness of preschool-aged children. This study examines the relationship between parental incarceration and school readiness among 3- to 5-year-old children in the United States. The current study employs data from 2016 to 2018 National Survey of Children's Health. The measure of school readiness is comprised of the following 4 domains: early learning skills, self-regulation, social-emotional development, and physical health & motor development. Multinomial logistic regression was used to examine the extent to which children were on-track across these key school readiness domains. Parental incarceration is associated with a reduction in the predicted probability of being on-track across all 4 domains. Furthermore, while only about 1 in 33 children without incarcerated parents will be on-track in none of the domains, approximately 1 in 6 children experiencing parental incarceration will be on-track in none of the domains. Ancillary analyses reveal that these results largely hold across items in each school readiness domain. Using a novel measure of school readiness, the current study finds parental incarceration is associated with reduced school readiness of preschool-aged children in the United States. Considering the vast benefits of early school readiness for development and academic achievement, our findings suggest a need for interventions that enhance school readiness among children who experience parental incarceration. Copyright © 2020 Academic Pediatric Association. Published by Elsevier Inc. All rights reserved.