Despite the clinical relevance of self-injurious thoughts and behaviors (SITB) among youth, little is known about the subset of youth most at-risk for SITB. This study examined the moderating roles of gender, racial/ethnic background, and school-level (and their interactions) on rates of SITB within a large (N = 2638, 52.2% female), ethnically-diverse sample of middle- and high-school youth in a relatively poor and underserved area of the Southern United States. Extending extant research in this area, findings indicated a significant interaction between gender and race for self-injurious behaviors, with African-American boys reporting higher rates than all other groups. Findings also indicated significant interactions between school-level and both gender and race for self-injurious thoughts. Whereas comparable levels of self-injurious thoughts were reported across middle- and high-schools for girls and African-American youth, the frequency of these thoughts was higher among both boys and White students in high-school (vs. middle-school). Results highlight the need for further research on SITB among diverse youth in underserved areas.