PurposeLGBTQ+ youth are at higher risk for poorer mental health. Studies are typically cross-sectional and categorize cisgender lesbian, gay, and bisexual (LGB) and transgender and gender diverse (TGD) youth as a combined group (i.e., LGBTQ+). There is a need for longitudinal studies that examine differences between LGB and TGD youth for a better understanding of their mental health needs. MethodsData come from a 4-wave longitudinal community-based study collected between 2011 and 2015. Hierarchical Linear Models examined trajectories of depressive symptoms and suicidality, comparing LGB and TGD youth. Between-person and within-person associations were examined, accounting for cumulative experiences of victimization, outness to family, and family acceptance in association with depressive symptoms and suicidality. ResultsThe study included a diverse sample of 543 LGB and 118 TGD youth. Although TGD youth had, overall, higher levels of depression and suicidality, both LGB and TGD youth experienced improvement in mental health. Youth who were more out and accepted in family were less depressed and suicidal than youth who were less out and accepted in family. Within individuals, when youth become more out and accepted in family, they concurrently reported less depressive symptoms. The accumulation of victimization experiences was associated with higher levels of depression and suicidality, and more depression for youth across time. DiscussionTGD youth face higher stigmatization than LGB youth, contributing to poorer mental health and disparities. Findings suggest that both LGB and TGD youth develop resilience despite victimization, and many find support within their families to cope with stigma.