PurposeTo compare baseline mental health symptoms and gender affirmation between Black/Latine versus White transgender/nonbinary youth (BLTY vs. WTY) and examine relationships between gender affirmation and mental health symptoms, and whether associations differed by race/ethnicity subgroup. MethodsBaseline data were analyzed from the gender-affirming hormone cohort of the Trans Youth Care United States Study—a 4-clinic site, observational study. Mental health symptoms assessed included depression, suicidality, and anxiety. Gender affirmation measures included the parental acceptance subscale from the perceived Parental Attitudes of Gender Expansiveness Scale-Youth Report; non-affirmation, internalized transphobia, and community connectedness subscales from the Gender Minority Stress and Resilience Measure–Adolescent; and self-reported living full time in affirmed gender. Fisher exact tests and independent sample t tests compared mental health symptoms and gender affirmation between subgroups. Logistic regression analyses evaluated associations between gender affirmation and mental health symptoms. Interaction analyses assessed differences in associations between subgroups. ResultsThe sample (mean age 16 years, range 12–20 years) included 92 BLTY (35%) and 170 WTY (65%). Subgroups had comparable prevalence of depression and anxiety symptoms. WTY had higher prevalence of lifetime suicidality (73% vs. 59%; p = .02). There were no differences in gender affirmation. Among the whole sample, higher parental acceptance decreased odds of depression symptoms. Not living in affirmed gender increased odds of depression symptoms. Higher non-affirmation and internalized transphobia increased odds of depression and anxiety symptoms and suicidality. Associations did not vary by subgroup. DiscussionBLTY and WTY had comparable mental health symptoms. For both subgroups, gender affirmation decreased odds of those symptoms.