Violence towards LGBTQ+ people is a topic of growing social and research interest. The scientific literature has mainly focused on victimization, with few studies exploring the factors that could trigger LGBTQ+ harassment perpetration in adolescents. Moral disengagement is postulated as a possible predictor variable as it has previously shown a relation with other forms of stigma-based harassment. However, there are no conclusive studies available in this regard in relation to LGBTQ+ harassment. The present study aims to fill this gap by analysing the predictive role of general and LGBTQ+ moral disengagement in LGBTQ+ harassment perpetration, differentiating between cisgender heteronormative and LGBTQ+ youths. A total of 1971 Spanish adolescents aged 12-18 years (M = 15.01; SD = 1.70; 24.30% LGBTQ+) participated in this cross-sectional study. The results showed that moral disengagement predicted LGBTQ+ harassment perpetration according to moral justifications and the characteristics of the population. This study provides relevant information for preventing LGBTQ+ harassment and identifying the role of moral disengagement therein.