<p>Sexual harassment perpetration is prevalent among adolescent boys and girls across offline and online environments. Given the serious consequences of sexual harassment, understanding ways to reduce its perpetration is crucial. To do so, this study explored the mediating role of moral emotions (responsibility and disengagement) in the association between pro-sexual harassment attitudes and sexual harassment perpetration. We considered different forms of sexual harassment and examined whether the mediation model showed differences based on gender. We conducted a cross-sectional study with 1177 adolescents (47.7% girls) from Andalusia in Spain. The mediation model explained around 5–8% of variability in girls and 5–13% in boys, with lower explained variance for online sexual harassment forms. The multi-group analysis showed gender differences in the model, in the path from pro-sexual harassment attitudes to disengagement, and from responsibility to verbal/visual sexual harassment perpetration. Direct effects of pro-sexual harassment attitudes on all sexual harassment forms were observed for both boys and girls. However, the hypothesized indirect effects via moral emotions received only partial support. Specifically, all indirect associations via responsibility were positive and significant for boys and girls. Indirect associations via disengagement were significant only for boys in offline sexual harassment (verbal/visual and physical). These findings indicate that pro-sexual harassment attitudes and moral emotions, particularly those of responsibility, are key correlates of sexual harassment perpetration for boys and girls. School interventions should be used for addressing the normalisation of lenient pro-sexual harassment attitudes and further support students’ emotional development.</p>