Previous studies have suggested that bullying may be contagious in adolescents. The present study examined whether ego depletion mediated the association between peer bullying and participant bullying and whether the mediating process was moderated by participant trait self-control. A sample of 2217 Chinese high school students (16.92 ± 0.94 years; 1068 boys and 1084 girls) were invited to fill in the questionnaires. The results reveal that after controlling for gender, grade and neuroticism, ego depletion partially mediates the positive relationship between peer bullying and participant bullying. Further, participant trait self-control moderates the relationship between peer bullying and participant bullying and that between peer bullying and participant ego depletion. That is, the strength of the contagion effect is lower in adolescents with high trait self-control compared to those with low trait self-control. In conclusion, this study provides empirical evidence of the contagion of bullying in adolescents. Limitations and implications for research and practice are discussed.