Aim: Most veterans have a successful transition to civilian life when they leave the military. However, there are some veterans who struggle to cope and adjust to the demands and challenges of civilian life. The aims of this research portfolio are: firstly to systematically review the published literature regarding the relationship between six emotion regulation strategies (acceptance, avoidance, problem-solving, reappraisal, rumination and suppression) and veteran mental health (PTSD, depression and anxiety); and secondly, to explore psychosocial factors (mental health, stigma, self-stigma, attitude towards and likelihood of help-seeking, experiential avoidance, reappraisal and suppression) that influence veteran adjustment from military to civilian life, and to determine which of these predict a poor transition. Method: A systematic review of the literature was conducted. Strict search criteria were applied and resulted in 23 studies which met the full inclusion criteria for the review. For the empirical study, 154 veterans across Scotland completed a set of questionnaires. Results: The systematic review highlighted significant relationships between the emotion regulation strategies and mental health disorders in the veteran population. The strength and direction of these relationships depended on the emotion regulation strategy and the mental health condition. The empirical study found that mental health, experiential avoidance and cognitive reappraisal predicted veteran adjustment difficulty. Discussion: There are clear links between veterans’ mental health, the way veterans regulate their emotions and the degree to which they adjust to civilian life. This has implications for how veterans are supported when they leave the Armed Forces, in terms of services and health professionals being able to better understand and support their difficulties, to facilitate their re-integration into civilian life.