Research on bullying victimization has expanded to specific forms of harassment based on discriminatory bias, which involve aggressive behavior targeting an individual's identity characteristics, such as sexual orientation and/or gender expression. Recent studies have documented elevated health risks associated with victimization based on homophobic bias, above and beyond general victimization. The aim of the current study was to test the unique contribution of homophobic victimization on adolescent non-suicidal self-injury (NSSI) and to analyze the buffering role of teachers and classmates support. Participants were 770 adolescents (55.5% females; "M"age = 15.35, SD = 1.62) enrolled in Italian public schools in grade nine (N = 483) and 12 (N = 287). All measures were collected during Spring 2016 using self-reported questionnaires. Zero-inflated Poisson regression analyses suggested that homophobic victimization had a unique contribution on NSSI frequency of engagement once initiated, but not on the probability of engaging in NSSI at least once. High classmates support was negatively associated with adolescents' engagement in NSSI. Furthermore, higher levels of classmates support were associated with a lower NSSI frequency only for youth who reported low levels of homophobic victimization. In contrast, the association between classmates support and NSSI frequency was nonsignificant when youth reported high levels of homophobic victimization. No significant effects were found for teachers support. Overall, our findings underscore the need to address the serious concern of homophobic victimization within schools and the importance of promoting healthy and positive identity development in adolescence.