ABSTRACT Research exploring developmental explanations for sexual and/or gender minority (i.e. SGM) mental health disparities often rely on adults’ retrospectively reported childhood adversity, leaving gaps in understanding how childhood adversity affects SGM mental health disparities during critical developmental periods and/or in contemporary youth. We tested the association between 459 12- to 17-year-old Canadian adolescents’ SGM status and mental health (i.e. life satisfaction, internalizing symptoms) and whether this was explained by indirect effects of peer and family adversity. Additionally, we examined developmental differences between early and middle adolescence. SGM status significantly predicted worse mental health. In an adjusted model, indirect effects through peer and family adversity were significant; the previously detected total effect of SGM status on life satisfaction disappeared and the effect on internalizing symptoms lessened. No significant developmental differences were detected. This suggests that mental health disparities are present in contemporary SGM youth and concurrent adverse experiences may underlie these disparities.