Introduction: The context of the current research involves relationships between traumatic or adverse childhood experiences, mental health variables and behavioural problems in delinquent adolescents. In the study we introduce the dimension of heterogeneity of antisocial behaviour to provide more insight into the role of internalising problems and borderline personality features as stemming from traumatic experiences and leading to aggression and rule-breaking behaviour in adolescents. Aim: Analysis of the mediating role of internalising problems and borderline personality features in the link between trauma experience and two forms of antisocial behaviour – aggression and rule-breaking behaviour. Methods: Eighty-eight adolescents (77.3% males, M_age = 14.69, SD = 1.51) assigned to the behaviour modification programme completed the Youth Self-Report (YSR 11/18), the Childhood Experiences Questionnaire (CEQ, adapted by Gervinskaite- Paulaitiene and Barkauskiene from the Adverse Childhood Experiences Questionnaire and the Adverse Childhood Experiences Score Calculator), and the Borderline Personality Features Scale for Children-11 (BPFSC-11). Statistical analyses included two multiple mediation models with two parallel mediators. Results: The study revealed that the link between traumatic experiences and aggression was mediated by borderline personality features, while internalising symptoms mediated the association of adverse childhood experiences and rule-breaking behaviour. Conclusions: Understanding the mediating role of internalising problems and borderline personality features in the link between childhood trauma and aggression as well as rule-breaking behaviour adds important knowledge to the understanding of the way leading towards antisocial behaviour, and could be used in the development of specified intervention programmes.