The authors examined the association of joint trajectories of ethnic identity and criminal offending to psychosocial maturity, gang membership, and Mexican-American affiliation among 300 Mexican-American male juvenile offenders from ages 14 to 22. There were two low-offending groups: one was the highest in ethnic identity and changing slightly with age and the other was the lowest in ethnic identity and stable with age. A third group displayed moderately declining offending and moderately stable ethnic identity. A fourth group displayed high-offending individuals with moderate, but increasing, levels of ethnic identity, who were initially lower in psychosocial maturity and more likely to be gang members. The findings highlight the need to contextualize theories of ethnic identity development. Abstract published by arrangement with John Wiley & Sons.