We investigate the relationship between adolescents’ construction of a transgression relating to a hypothetical temptation and bystander behaviour and bullying (offline and online). A total of 331 Swiss eighth graders completed an electronic questionnaire on bystanding, bullying, moral disengagement, and empathy. Moral functioning was assessed in a hypothetical scenario, using different moral judgements (deontic and self‐judgement, judging the transgression; paper‐and‐pencil measure). Cluster analyses were used to identify patterns of moral functioning. For the open situation (deontic and self‐judgement), happy transgressors, happy moralists, ashamed moralists, and indifferent moralists were differentiated, and for the transgression (accomplished deed) moralists and happy opportunists. The analyses yielded significant differences between the different cluster groups. Happy transgressors (open situation) reported higher levels of assisting the bullying than unconcerned moralists. Happy transgressors also reported lower levels of helping than ashamed and happy moralists. Opportunists (accomplished deed) reported higher levels of assisting the bullying, offline bullying, and lower levels of helping the victim. The multivariate GEE analyses showed that happy transgressors reported higher levels of assisting the bully and online bullying than the moralist groups (open situation). The study shows that adolescents who construct a favourable interpretation of yielding to temptation in a hypothetical scenario displayed higher levels of both assisting the bully and online bullying, emphasizing the need for incorporating targeted moral education in bullying prevention.