To examine the development of religious identity during the teenage years, adolescents (N = 477) from Latin American, Asian, and European backgrounds completed questionnaires in the 10th, 11th, and 12th grades (10th grade age: M = 15.81, SD = 0.36). Results indicated that religious identity remained stable across high school whereas religious participation declined. Even after controlling for ethnic differences in religious affiliation, socioeconomic background, and generational status, adolescents from Latin American and Asian backgrounds reported higher levels of religious identity and adolescents from Latin American backgrounds reported higher rates of religious participation. Within individual adolescents, changes in religious identity were associated with changes in ethnic and family identities, suggesting important linkages in the development of these social identities during adolescence.