Prior studies have reported generational declines in the ages at which sexual minority people first experience (e.g., first awareness of same-sex attraction, self-realization of a sexual minority identity, same-sex sexual behavior, and disclosure); yet such studies have relied on retrospective data from adults that may conflate maturational age influences with cohort influences. In the current study, we disentangled age from cohort influences on milestone timing by harmonizing secondary data from three large and diverse datasets of cisgender sexual minority adolescents ages 15-19 years old ( = 1,310; M = 17.34, SD = 1.30) collected at three distinct sociohistorical eras of sexual diversity (the 1990s, the 2000s, and the 2010s). With three age-matched but sociohistorically distinct cohorts, we compared milestone timing and pacing across cohorts, as well as subgroup differences among adolescents with social identities at the intersections of cohort with sex, sexual identity, and race/ethnicity, respectively. A series of multiple regression models suggested that more recent generations of sexual minority adolescents reported earlier ages of first self-identification and disclosure than less recent generations; however, adolescents reported similar ages of awareness of same-sex attraction and same-sex sexual behavior across cohorts. Insights from this study build support for cohort differences in the timing of some sexual identity developmental processes and underscore the importance of accounting for both maturational age and sociohistorical change when measuring the sexual identity development processes of sexual minority youth.