<p>Attrition rates in rehabilitative programmes for violent behaviour are concerning as exiting from treatment may have implications for individuals (e.g., further offending, diminished quality of life), the organisation providing the treatment (e.g., cost, ineffectiveness), and for the society (e.g., safety, trust in the criminal justice system). Therefore, it is necessary to consider factors that may hinder the progress and completion of the treatment of violent offending. This study aimed to extend Te Hiwi's (2020) findings on negative relationship between childhood traumatic events and treatment outcomes, by exploring the role of maladaptive personality traits in this relationship. The study was based on retrospective, file-based data of 417 men who attended the high-intensity rehabilitation programme in New Zealand. Binomial and logistic regression models predicting treatment progress and outcome as well as a structural equation model showed that maladaptive personality traits – antisocial, borderline, and psychopathic – had overall no significant role in the relationship between trauma and treatment progress, despite men who were high on psychopathic traits being less likely to complete the treatment. Traumatic childhood events had a negative impact on treatment progress. In addition, treatment progress in the presence of all types of trauma was a less frequent pattern configuration than statistically expected. These findings reiterate the need for further research on the underlying mechanisms in the relationship between childhood trauma and treatment of violent offending, and self-regulation was suggested as one such mechanism.</p>