Cognitive behavioral therapies have positive effects on anger and aggression; however, individuals differ in their response to treatment. The authors previously found that dynamic factors, such as increases in readiness to change, are associated with enhanced outcomes for violence reduction training. This study investigated how less dynamic factors, specifically Cluster B personality traits, moderate the effects of violence reduction training. The authors used mixed modeling to fit growth curves to 14 weeks of anger strategies data and evaluated whether the presence of Cluster B traits affected pretreatment anger levels and rates of change. As expected, overall levels of negative anger strategies decreased across the 14-week treatment. Participants with antisocial, borderline, and histrionic personality features reported higher rates of negative anger strategies, whereas those with narcissistic personality features reported fewer negative anger strategies. Those with antisocial personality features improved at a rate similar to the overall trend of those without Cluster B traits. Those with borderline and histrionic features improved at an accelerated rate. (Contains 4 tables and 1 figure.)