Lesbian, gay, bisexual, transgender/nonbinary, and queer (LGBTQ +) adolescents experience considerable disparities in dating violence and sexual assault victimization relative to heterosexual and cisgender peers. These disparities may be driven in part by the disruptive effects of heterosexism and cissexism on school-based and family relationships. To quantify the potential roles of these processes and identify priorities for prevention efforts, we estimated the extent to which dating violence and sexual assault victimization in LGBTQ + adolescents could be reduced by eliminating sexual orientation and gender modality inequities in school adult support, bullying victimization, and family adversity. We analyzed data from a cross-sectional, population-based survey of high school students in Dane County, Wisconsin (N = 15,467; 13% sexual minority; 4% transgender/nonbinary; 72% White) using interventional effects analysis, adjusting for grade, race/ethnicity, and family financial status. We found that eliminating inequities in bullying victimization and family adversity could significantly reduce dating violence and sexual assault victimization in LGBTQ + adolescents, particularly sexual minority cisgender girls and transgender/nonbinary adolescents. For instance, eliminating gender modality inequities in family adversity could reduce sexual assault victimization in transgender/nonbinary adolescents by 2.4 percentage points, representing 27% of the existing sexual assault victimization disparity between transgender/nonbinary and cisgender adolescents (P < 0.001). Results suggest that dating violence and sexual assault victimization in LGBTQ + adolescents could be meaningfully reduced by policies and practices addressing anti-LGBTQ + bullying as well as heterosexism- and cissexism-related stress in LGBTQ + adolescents' families.