Ethnic/racial disparities in DNA methylation age profiles have been commonly captured in relatively small, community samples of individuals from a single age group. Whether such findings extend to large, national samples of individuals is unclear, especially in studies covering multiple developmental periods, including childhood, adolescence, and adulthood. These DNA methylation profiles linked to age can be used to derive epigenetic clocks as indices of premature aging and inform possible cellular mechanisms linking ethnic/race-related adversities and ethnic/racial disparities in mortality and morbidity. Thus, the present descriptive study leveraged data from 3,349 individuals who participated in one of two national and ethnically/racially diverse studies, the Future of Families and Child Wellbeing (FFCW) study and the Midlife in the United States (MIDUS) Study. The FFCW study included repeated measures of children’s DNA methylation age profiles at age 9 (i.e., childhood) and age 15 (i.e., adolescence), and the MIDUS study included participants’ DNA methylation profiles at a single wave during adulthood. Results showed that ethnic/racial minorities exhibited more accelerated within-person changes in the GrimAge, PhenoAge, and Dunedin epigenetic clocks across childhood and adolescence and more accelerated between-person differences in the Dunedin epigenetic clock during adulthood. Collectively, both studies show robust ethnic/racial disparities in DNA methylation age profiles and underscore the need to address institutional racism and ethnocentrism in the United States.