Social gender transition is an increasingly accepted intervention for gender variant children and adolescents. To date, there is scant literature comparing the mental health of children and adolescents diagnosed with gender dysphoria who have socially transitioned versus those who are still living in their birth-assigned gender. We examined the mental health of children and adolescents referred to the Gender Identity Development Service (GIDS), a specialist clinic in London, UK, who had socially transitioned (i.e., were living in their affirmed gender and/or had changed their name) versus those who had not socially transitioned. Referrals to the GIDS were aged 4–17 years. We assessed mental health correlates of living in one’s affirmed gender among 288 children and adolescents (208 birth-assigned female; 210 socially transitioned) and of name change in 357 children and adolescents (253 birth-assigned female; 214 name change). The presence or absence of mood and anxiety difficulties and past suicide attempts were clinician rated. Living in role and name change were more prevalent in birth-assigned females versus birth-assigned males. Overall, there were no significant effects of social transition or name change on mental health status. These findings identify the need for more research to understand how social transition influences mental health, including longitudinal studies that allow for more confident inferences to be made regarding the relationship between social transition and mental health in young people with gender dysphoria.