The purpose of this study was to examine the mediating effects of aggression and neuroticism in the relationship between childhood bullying and antisocial, borderline personality traits in adulthood. Totally, 696 adults completed self-report questionnaires, which included the Perpetration-Victimization of the Bullying Scale, the Diagnostic Test for Personality Disorder, the Korean Version of the Aggression Questionnaire (K-AQ), and the Korean Version of the Big Five Inventory (K-BFI). The study’s findings indicated that aggression partially mediated the relationship between childhood bullying behavior and antisocial personality, while aggression and neuroticism fully mediated the relationship between victimization of childhood bullying and antisocial personality. Similarly, aggression also partially mediated the relationship between childhood bullying behavior and borderline personality, while both aggression and neuroticism partially mediated the relationship between victimization of childhood bullying and borderline personality. In addition, the relationship between bullying victimization and antisocial, borderline personality was mediated by emotional aggression, not by physical or verbal aggression. These findings supported our hypothesis that childhood bullying contributed to the development of antisocial and borderline personality traits, which were mediated by aggression or neuroticism. Yet, the mediating role of neuroticism was revealed only in the relationship between victimization and borderline personality. This suggests that intervention programs to reduce aggression and neuroticism could be beneficial in preventing the development of antisocial, borderline personality traits among individuals who have experienced childhood bullying.