Social identity, including identification with one's ethnic group, is an important aspect of social development. However, little is known about the subjective meaning associated with social group memberships, particularly during middle childhood. Using second- and fourth-graders responses to an open-ended question, we explored the meaning of ethnic identity with a sample of Chinese, Dominican, Russian, White, and Black American children. Analyses revealed that middle childhood is an active period for meaning making as children described the ethnic identity to include ideas such as language, physical appearance, pride, relative social position, and culture. While there were few differences in the ethnic identity meaning responses of second- and fourth-grade children, the meaning of ethnic identity varied considerably across the ethnic groups underscoring how the unique features and experiences of different ethnic groups shapes the subjective meaning of ethnic identity. These findings align with prior research on the meaning of ethnic identity among adults and adolescents and offer insight for future research regarding the conceptualization and measurement of the meaning of social group membership.