OBJECTIVE 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).