In general, research shows that participating in sport and PA has positive effects on young people’s mental health. However, this research has relied on overwhelmingly cisgender samples of youth; the impacts of sport and physical activity in the lives of transgender (TGD) adolescents, specifically, are understudied. Descriptive research has not tracked TGD youths’ participation in sport over time, and it is unclear whether participating in sport and PA has the same benefits for TGD teens as for teens in general. We will address research gaps by 1) evaluating trends in TGD adolescents’ sport and PA participation from 2016 to 2019 to 2022, 2) testing relationships between sport, PA, and mental health concerns among TGD youth, and 3) understanding how team sport participation impacts the lives and mental health of TGD adolescent athletes using interviews with them, their parents, their coaches, and their cisgender teammates. Our research will provide much-needed pictures of trends in participation over recent years and of TGD youths’ mental health as it relates to sport and PA. We will share our work through academic manuscripts, a fact sheet, and a policy brief to provide much-needed data to researchers, policymakers, and advocates.