As bullying episodes generally occur in the presence of other peers, encouraging all children to stand up for those being victimized – rather than watching or doing nothing – has become a key objective of many intervention programs. Anti-bullying programs like the KiVa program try to reduce bullying in many ways, including increasing defending behaviours among students (for example, telling the bully to stop, or comforting the victim). This has raised several questions over the years: How does the program successfully increase defending? Specifically, what changes in the minds of the children who have participated in the program to convince them to stand up for their victimized peers? And importantly, what are the potential consequences for the children who defend others? Is it safe or does it make them more vulnerable to being victimized or to developing mental health issues? A series of recent studies have now provided answers to these questions.