This study investigated the relationship between maladaptive personality traits operationalized by the Alternative Model for Personality Disorders (AMPD) domains and the presence of dual harm. Earlier research has primarily examined associations between personality traits and either self-harm or aggression. These studies indicated an association between maladaptive personality traits and harm behaviour but little research has investigated their relationship with dual harm. To investigate the relationship between dual harm and maladaptive personality traits this study used the Personality Inventory for DSM-5–Brief Form (PID-5-BF) to compare three groups: self-harm, other-harm and dual harm. The five AMPD domains assessed are negative affectivity, detachment, antagonism, disinhibition, and psychoticism. Separate Kruskal-Wallis tests and Dunn’s post-hoc analyses found that the dual harm group scored significantly higher than both sole harm groups on antagonism, disinhibition and psychoticism. The dual harm group scored significantly higher than the self-harm group on the negative affectivity and detachment domains. These findings suggest that people who engage in dual harm present with more personality dysfunction overall. Further research is needed to investigate this relationship and underlying mechanisms.