Current approaches in Dutch mental health care institutions towards inpatients' aggression have focused predominantly on environmental factors, such as training the staff in aggression management. However, personality traits might be an important factor in patients' aggressionas shown by incidents in the wards. This study explores the influence of dysfunctional impulsivity and alexithymia on psychiatric patients' aggressive behavior, through self-reports and through involvement in aggressive incidents. Personality traits influencing patients' aggression emphasize the importance of a more direct approach to their aggression. Clinical patients at Dutch mental health care institution Emergis (n = 84) filled out questionnaires about their aggressiveness (using Buss and Perry's Aggression Questionnaire Short Form), dysfunctional impulsivity and alexithymia. Multiple regression analyses indicated that dysfunctional impulsivity positively related to self-reported aggressive behavior. The relationship, however, could not be confirmed for inpatients' aggression as reported by the staff on the wards. Unexpectedly affective alexithymia negatively related to hostility. Gender differences in self-reported aggression were found. Female patients showed higher levels of hostility. Regression analyses indicated that the male gender positively related to physical aggression. Findings emphasize the importance of a new approach in Dutch mental health care, in which patients may engage in aggression-regulation training programs.