The current study examines the role of ethnic-racial socialization (ERS) and maternal autonomy granting in predicting ethnic-racial identity (ERI) exploration, resolution, and affirmation trajectories in a sample of Mexican-origin girls (N = 338) in early and middle adolescence at Wave 1. Latent growth curve analyses showed significant growth in ERI exploration, resolution, and affirmation over 3.5 years. ERS, autonomy granting, and their interaction were associated with ERI trajectories. Results also indicated significant differences between early and middle adolescents in the association between ERS, autonomy granting, and ERI exploration trajectories. Findings demonstrate the importance of concurrently examining contextual and developmental predictors of ERI formation. In addition, ERS may be particularly important for ERI development among early adolescents, whereas autonomy processes and development may play a more prominent role during middle adolescence.