Objective. In this article, we use data from the Early Childhood Longitudinal Survey—Kindergarten Cohort to analyze the links between preschool attendance and the school readiness of children of immigrants. Methods. Using data from the Early Childhood Longitudinal Survey—Kindergarten Cohort, we estimate multivariate regression models for the effects of preschool on school readiness for children of immigrants and children of natives. Results. We find that children whose mothers were born outside the United States are less likely to be enrolled in school or center-based preschool programs than other children. We find that preschool attendance raises reading and math scores as much for children of immigrants as it does for other children. Attending preschool also raises the English-language proficiency of children of immigrants. Although not the main focus of our study, we examined the effects of Head Start, and found that this program improves children's English proficiency, with especially large effects for children of immigrants whose mothers have less than a high school education; in this latter group, Head Start also improved math scores. Conclusions. Given that preschool benefits children of immigrants as much as it does children of natives and given that children of immigrants are less likely to be enrolled, our findings strongly suggest that enrolling more children of immigrants in preschool would help reduce inequality in skills at school entry.