OBJECTIVE: Transgender children who have socially transitioned, that is, who identify as the gender "opposite" their natal sex and are supported to live openly as that gender, are increasingly visible in society, yet we know nothing about their mental health. Previous work with children with gender identity disorder (GID; now termed gender dysphoria) has found remarkably high rates of anxiety and depression in these children. Here we examine, for the first time, mental health in a sample of socially transitioned transgender children. METHODS: A community-based national sample of transgender, prepubescent children (n = 73, aged 3-12 years), along with control groups of nontransgender children in the same age range (n = 73 age- and gender-matched community controls; n = 49 sibling of transgender participants), were recruited as part of the TransYouth Project. Parents completed anxiety and depression measures. RESULTS: Transgender children showed no elevations in depression and slightly elevated anxiety relative to population averages. They did not differ from the control groups on depression symptoms and had only marginally higher anxiety symptoms. CONCLUSIONS: Socially transitioned transgender children who are supported in their gender identity have developmentally normative levels of depression and only minimal elevations in anxiety, suggesting that psychopathology is not inevitable within this group. Especially striking is the comparison with reports of children with GID; socially transitioned transgender children have notably lower rates of internalizing psychopathology than previously reported among children with GID living as their natal sex.