Bullying is often followed by short-term and long-term undesirable psychosocial consequences. Both victims and perpetrators of bullying tend to have high numbers of physical and psychological symptoms. In order to prevent bullying and its aversive results, it is important to formulate and test theories of bullying. This article investigates the usefulness of defiance theory in the explanation of the bullying of siblings in families and peers in schools. Questionnaires were completed by 182 children aged 11 to 12 in 10 primary schools in Nicosia, Cyprus. The authors followed a vignette-based methodology to investigate children's defiant behavior. Children were given a hypothetical scenario in which the perpetrator is sanctioned by the parents and were then asked questions that aimed to investigate defiant or compliant reactions to the sanctions imposed. The type of child in the vignette was experimentally manipulated so that children could make inferences regarding his/her intentionality of wrongdoing. The results indicate that defiance theory is useful in explaining bullying behavior. The main implication from our research is that defiance theory can assist teachers and practitioners in implementing whole-school restorative justice approaches to reduce bullying in schools. (Published Abstract)