Military service and ex-service personnel commonly experience difficulties with anger. The COVID-19 pandemic had several negative consequences upon social, economic and health factors that influence anger. This study aimed to explore 1) levels of anger in an ex-serving military cohort during the COVID-19 pandemic, 2) self-reported changes in anger compared to pre-pandemic levels, and 3) identify sociodemographic characteristics, military characteristics, COVID-19 experiences and stressors associated with anger. UK ex-service personnel (N=1,499) completed the Dimensions of Anger Reactions 5-item measure within an existing cohort study. Overall, 14.4% reported significant difficulties with anger and 24.8% reported their anger worsened during the pandemic. Anger was associated with factors such as financial difficulties, extra/new caring responsibilities, and COVID-19 bereavement. Endorsing more COVID-19 stressors was associated with higher odds of anger difficulties. This study highlights the impact of the pandemic on ex-service personnel, including a strain on family/social relationships and financial hardship, which affected anger.