The overarching goal of this dissertation was to contribute to the field’s understanding of young children’s development of ethnic-racial identification. In particular, Study 1 presented the adaptation of three measures that are developmentally appropriate for assessing young children’s ethnic-racial attitudes, ethnic-racial centrality, and ethnic-racial knowledge, and tested the psychometric properties of each measure. Findings from Study 1 provided limited initial support for the construct validity and reliability of the measures; importantly, there were many differences in the descriptives and measurement properties based on the language in which children completed the measures. In addition to measurement of ethnic-racial identification, Study 2 used the measures developed in Study 1 and tested whether Mexican-origin mothers’ adaptive cultural characteristics (i.e., ERI affirmation, ethnic-racial centrality, and involvement in Mexican culture) when children were 3 years of age predicted greater cultural socialization efforts with children at 4 years of age and, in turn, children’s ethnic-racial identification (i.e., children’s ethnic-racial attitudes, ethnic-racial centrality, ethnic-racial knowledge, and identification as Mexican) at 5 years of age. Furthermore, children’s characteristics (i.e., gender and skin tone) were tested as moderators of these processes. Findings supported expected processes from mothers’ adaptive cultural characteristics to children’s ethnic-racial identification via mothers’ cultural socialization across boys and girls, however, relations varied by children’s skin tone. Findings highlight the important role of children’s individual characteristics in cultural socialization and young children’s developing ethnic-racial identification over time. Overall, given the paucity of studies that have examined ethnic-racial identification among young children, the results from Study 1 and Study 2 have the potential to stimulate growth of knowledge in this area.