Background: Theory of mind (ToM) allows the understanding and prediction of other peoples behaviours based on their mental states (e.g. beliefs). It is important for healthy social relationships and thus may contribute towards childrens involvement in bullying. The present study investigated whether children involved in bullying during early adolescence had poor ToM in childhood. Method: Participants were members of the Environmental Risk (E-Risk) Longitudinal Twin Study, a nationally representative sample of 2,232 children and their families. We visited families when children were 5, 7, 10 and 12 years. ToM was assessed when the children were 5 years using eight standardized tasks. Identification of those children who were involved in bullying as victims, bullies and bully-victims using mothers', teachers' and children's reports was carried out when they were 12 years' old. Results: Poor ToM predicted becoming a victim (effect size, d = 0.26), bully (d = 0.25) or bully-victim (d = 0.44) in early adolescence. These associations remained for victims and bully-victims when child-specific (e. g. IQ) and family factors (e. g. child maltreatment) were controlled for. Emotional and behavioural problems during middle childhood did not modify the association between poor ToM and adolescent bullying experiences. Conclusion: Identifying and supporting children with poor ToM early in life could help reduce their vulnerability for involvement in bullying and thus limit its adverse effects on mental health.