Transgender and gender non-conforming (TGNC) individuals are at a high risk of adverse mental health outcomes due to minority stress-the stress faced by individuals categorised as stigmatised social minority groups. This systematic review sought to summarise the key mental health findings of the research on TGNC individuals in mainland China. We also aimed to consolidate research on the topic, identify specific mental health disparities, and offer new perspectives for future research to inform both policy and clinical practice. An extensive search of the literature, published in English and Chinese, was done between Jan 1, 1990, and Aug 1, 2021, using PubMed, PsycINFO, Scopus, Wanfang (in Chinese), and CNKI (in Chinese). Overall, two qualitative and 28 quantitative articles were identified. The quantitative findings showed a high prevalence of mental health problems, such as depression, anxiety, substance use disorders, and stress-related issues, and greater disparities in psychological wellbeing. High prevalence is also reported in suicidality and self-harm behaviours in this group. Across the two qualitative studies, attributable factors included gender-related discrimination, barriers to accessing health services, low social support, decreased knowledge and awareness of HIV prevention, and demographic characteristics-such as marital status, educational level, and gender identity. This Review also found little evidence of gender-affirming care and mental health interventions in mainland China. Following from these results, the next step is to integrate multi-level, socialpsychological interventions with education to reduce cultural stereotypes and transphobia in mainland China. Political and social implications are also discussed to inform a standard set of guidelines for transgender-inclusive health-care services, including advocating for funding to create these special care programmes and services.