Background: Previous research has consistently reported high rates of mental health symptomatology and lower social support in young treatment seeking transgender individuals. However, these studies have failed to distinguish between transgender people who identify within the gender binary and those who identify as non-binary. Aims: This study aimed to compare levels of mental health symptomatology (anxiety, depression, and non-suicidal self-injury behaviour) and social support of treatment seeking non-binary transgender young individuals with those self-identified as binary transgender young individuals. All participants were attended a national transgender health service in the UK during a 2 years period. Measures: Age and gender identity descriptors were collected, as well as clinical measures of anxiety and depression (Hospital Anxiety and Depression Scale), self-esteem (The Rosenberg Self-Esteem Scale), non-suicidal self-injury (Non-Suicidal Self-Injury: Treatment Related), and social support (Multidimensional Scale of Perceived Social Support). Results: A total of 388 young people, aged 16-25 years, agreed participation; 331 (85.3 %) identified as binary and 57 (14.7 %) as non-binary. Analysis of the data showed the nonbinary group experienced significantly more anxiety and depression and had significantly lower self-esteem that the binary group. There were no significant differences between groups in the likelihood of engaging in non-suicidal self-injury behaviour or levels of social support. Conclusions: Non-binary identifying treatment seeking transgender youth are at increased risk of developing anxiety, depression and low self-esteem compared to binary transgender youth. This may reflect the even greater barriers and feelings of discrimination that may be faced by those whose identity does not fit the notion of binary gender that is pervasive in how society views both cis-and transgender populations.