Language is vital for social interaction, leading some to suggest early linguistic ability paves the way for good adolescent mental health. The relation between age-5 vocabulary and adolescent internalizing symptoms was examined in two U.K. birth cohorts that are nationally representative in terms of sex, ethnicity, and socioeconomic status: the 1970 British Cohort Study (BCS; N = 11,640) and the Millennium Cohort Study (MCS born ~2001; N = 14,754). In the BCS, no relation between receptive vocabulary and age-16 self-reported symptoms was observed ([beta] = 0.00 [-0.03; 0.03]). In the MCS, better expressive vocabulary was associated with "more" age-14 self-reported symptoms ([beta] = 0.05 [0.02; 0.07]). The direction of this effect was reversed for parent-reported symptoms. All effect sizes were small. The relation between childhood vocabulary and internalizing symptoms varies by generation and reporter.