Objectives: Sexual minority adolescents have previously been found to experience disparities in self-injurious thoughts and behaviors (SITBs) compared to heterosexual adolescents. However, there is a paucity of data on SITBs amongst children. Thus, the aim of the current study is to assess the prevalence of SITBs in a large sample of U.S. children and to test whether rates vary by sexual orientation. Methods: Data were drawn from the 2.0 baseline release of the Adolescent Brain Cognitive Development (ABCD) study. The full sample included 11,777raw 9–10-year-old children (sexual minority n = 150raw). Children completed a computerized version of the youth Kiddie Schedule for Affective Disorders and Schizophrenia (KSADS-5), including items assessing suicide ideation, suicide attempts, and nonsuicidal self-injury (NSSI). Unadjusted and adjusted models compared the prevalence of outcomes by sexual orientation. Models also compared the co-occurrence of NSSI and suicide ideation by sexual orientation. Results: Across all outcomes, sexual minority children reported elevated prevalence rates compared to heterosexual children, with odds ratios ranging from 4.4 to 6.5. Among children who reported NSSI, a greater proportion of sexual minority versus heterosexual children reported co-occurring suicide ideation (OR = 3.8). Conclusions: In a large sample of 9–10-year-old U.S. children, sexual orientation disparities emerged across NSSI, suicide ideation, and suicide attempts. Results indicate that sexual minority children are a vulnerable population for SITBs. Inclusion of children in prevention programs is encouraged. (PsycInfo Database Record (c) 2021 APA, all rights reserved)