Prevalence rates of anger and aggression are often higher in military personnel, so it is important to understand more about why this is and factors with which they are associated. Despite this, there is little evidence relating to anger and aggression in UK veterans who are seeking treatment for mental health difficulties such as PTSD. This study investigated the prevalence rates of anger and aggression in this population, as well as the associations between anger and aggression, and various sociodemographic, functioning and mental health variables. A cross-sectional design was used, with participants completing a battery of self-report questionnaires. Prevalence rates for significant anger and aggression were 74% and 28% respectively. Both women and those over 55 were less likely to report difficulties. Those with high levels of PTSD and other mental health difficulties were more likely to report anger and aggression. Other factors related to anger and aggression included childhood adversity; unemployment due to ill health; and a perceived lack of family support. Findings show that veterans who are seeking support for mental health are likely to experiencing significant difficulties with anger and aggression, especially if they have co-morbid mental health difficulties. The associations between anger and aggression and other variables has implications for the assessment and treatment of military veterans.