Although research investigating ethnic differences in mental health has increased in recent years, we know relatively little about how mental health trajectories vary across ethnic groups. Do these differences occur at certain ages but not others? We investigate ethnic variation in trajectories of depressive symptoms, and we examine the extent to which disadvantages in family background, high school experiences, and adult characteristics explain these diferences. Employing random-coefficient modeling using the National Longitudinal Survey of Youth, we find that blacks and Hispanics experience higher symptom levels in early adulthood in comparison to whites, but equivalent levels by middle age. Ethnic differences remained in early adulthood after including all covariates, but those differences were eliminated by middle age for Hispanics after controlling for demographics only, and for blacks after accounting for the age-varying relationship between income and depressive symptoms. These results highlight the importance of integrating a life course perspective when investigating ethnic variations in mental health.