As the population in the United States continues to become more diverse, early childhood programs serving our nation's youngest citizens strive to meet the needs of families from different cultural backgrounds. Despite the established importance of ethnic-racial socialization in the early social and cognitive development of young children, parents and teachers seldom discuss issues related to race and ethnicity with preschool children. Using propositions within the bioecological and developmental niche models, critical race theory, and frameworks that focus on the socialization of children from diverse ethnic-racial backgrounds, the current study examined differences between parents' and teachers' use of ethnic-racial socialization and links between match or mismatch and children's self-regulation. The sample consisted of 63 three- to five-year-old children from diverse ethnic-racial backgrounds, their primary caregivers, and their Head Start teachers, all residing in a mid-sized city in Upstate New York. Results indicate that parents use ethnic-racialization more than teachers, both home and early childhood environments had similar numbers of cultural items, and parents and teachers used egalitarian messages the most compared to other modes of socialization. Bayesian analyses revealed significant ethnic-racial group differences in the utilization of preparation for bias and cultural socialization messages. African American parents used preparation for bias and cultural socialization at higher rates than parents of European American children and those in the combined ethnic group. Match in caregivers' and teachers' use of egalitarian messages was associated with higher self-regulation. A greater difference between ethnic-racial socialization in home and school physical environments was also surprisingly linked to higher self-regulation scores. Findings highlight the importance of ethnic-racial socialization in Head Start children's early social development and may be useful in informing early childhood practices relating to cultural continuity. (author abstract)