Objectives <p>Although past studies have identified sex differences in child maltreatment experiences and poor mental and physical health‒related outcomes, more research is needed to understand child maltreatment among sexual minorities (i.e., those who identify as other than heterosexual) and how child maltreatment and sexual identity are related to depression, anxiety, and at-risk alcohol and cannabis use among emerging adults.</p> Methods <p>Data were drawn from the longitudinal Well-Being and Experiences (WE) Study collected from 2017 (14 to 17&#xa0;years) to 2022 (18 to 23&#xa0;years) from Manitoba, Canada (<i>n</i> = 584). Descriptive statistics and logistic regression models were computed.</p> Results <p>Compared to heterosexual or straight sexual identity: homosexual, gay or lesbian; bisexual; and different or other identity were associated with an increased likelihood of experiencing child maltreatment, with the most robust relationships for bisexual identity and all child maltreatment outcomes. Indicating “I don’t know” for sexual identity compared to heterosexual identity was associated with 7.45 increased odds of exposure to intimate partner violence in adjusted models. Bisexual identity compared to heterosexual identity had the most robust association, with increased odds of depression, anxiety, at-risk alcohol use, and at-risk cannabis use. Findings provide some evidence to suggest that trends may be worse for some mental health and substance use outcomes among sexual minorities who also experience child maltreatment.</p> Conclusion <p>Preventing child maltreatment among all children, including youth identifying as other than heterosexual, is a public health priority. Such efforts will work towards optimizing mental health and reducing substance use in early adulthood.</p>