This study assesses how beliefs about aggression and personality can predict engagement in intra-group bullying among prisoners. A sample of 213 adult male prisoners completed the DIPC-SCALED (bullying behavior), the EXPAGG (beliefs toward aggression), and the IPIP (a five-factor measure of personality). It was predicted that bullies would hold greater instrumental beliefs supporting the use of aggression than the other categories, with perpetrators reporting lower scores on agreeableness, conscientiousness, and openness to experience, and higher scores on neuroticism (i.e. low scores on emotional stability) than the remaining sample. Bullies and bully-victims endorsed greater instrumental aggressive beliefs than the victim category. Only one perpetrator group, bullies were predicted by reduced levels of agreeableness and increased levels of neuroticism, whereas bully/victims were predicted by decreased levels of neuroticism. Limitations of this study and directions for future research are discussed.