Abstract Transgender and gender-diverse (TGD) individuals are at a greater risk for various poor mental and behavioral health outcomes than cisgender individuals, including higher rates of suicide, psychiatric diagnoses, and behavioral health problems. For example, research has documented a seven-fold increased risk for lifetime suicide attempts among young TGD people, compared with the general population. Less is known about the age of onset of such mental and behavioral health disparities and how these disparities may vary across other intersectional socio-demographic variables. It has been well-documented that trans and gender-diverse individuals often encounter discrimination and transphobia across various social, educational, professional, administrative, and healthcare settings. This discrimination, as highlighted in the literature, frequently poses obstacles to accessing both general and trans-specific healthcare services due to experiences of discrimination (e.g., misgendering, refusal of care, lack of adequate services). The right and ability to self-determine and the accessibility to gender-affirming care without discrimination are key to closing the gap in TGD individuals’ mental and behavioral health outcomes, and for them to live authentically and thrive. Tailored and affirming mental and behavioral health interventions to reduce these health inequities are pivotal for TGD individuals to achieve the highest attainable standard of physical and mental health: a key fundamental human right. Considerable gaps in the literature remain concerning the onset and determinants of gender identity-based health disparities and healthcare approaches that are respectful, inclusive, non-pathologizing, and grounded in human rights principles for TGD individuals. This workshop intends to address these knowledge gaps by delving into the mental and behavioral health needs of TGD individuals. The workshop seeks to further foster dialogue on strategies to overcome resistance to implementing approaches that uphold the human rights and well-being of these communities. Dr. Richard Bränström (Karolinska Institutet) will present a study that explores the age at which gender identity-based disparities in psychiatric diagnoses and treatment can be first identified. Dr. Gonzales (Vanderbilt University) will examine disparities in mental health and social determinants of health among TGD individuals with private insurance. Dr. Moleiro (Lisbon University Institute) will review TGD persons’ ways of identifying with the choices and trajectories in social, legal, and affirmative healthcare processes in Portugal. Dr. Lelutiu-Weinberger (Columbia University School of Nursing) will present findings from a study that assessed tobacco use and cessation attitudes, facilitators, and barriers to quitting, and intervention components and delivery modality acceptability among TGD individuals, as well as sexual minority individuals, in Romania to inform a tailored and affirming smoking cessation intervention. Key messages • Transgender and gender-diverse are at increased risk for a variety of poor mental and behavioral health compared with the general public. • There is a critical need to foster healthcare services for transgender and gender-diverse individuals that are tailored and affirming.