Abstract: Alcohol misuse - defined as consuming more than 14 units of alcohol per week - is a well-established problem among veterans. This study investigated the change in quality of life among help-seeking UK veterans who completed a 28-day brief alcohol intervention delivered via a digital smartphone application (called DrinksRation) and have previously sought clinical help for a mental health disorder. This study was a secondary outcome analysis of data collected during a randomised control trial. In total, 123 UK veterans participated in the study and were randomly allocated to either the intervention or control arm. Participants completed self-report questionnaires regarding their alcohol use and quality of life (WHOQOL-BREF) at baseline, day 28 (end of intervention), day 84, and day 168. At the primary endpoint (day 84), we found significantly greater improvements in the intervention arm compared to the control arm for psychological quality of life (Cohen's d = 0.47), and environmental quality of life (d = 0.34). However, we observed no statistically significant differences between the intervention and control arm for social relationships and physical quality of life. Further, for day 168 we found no significant differences. Findings suggest that DrinksRation can increase quality of life among help-seeking veterans who have previously sought help for a mental health disorder, but the increases were modest and restricted to certain domains. Additional treatment may be needed for long-term and sustained improvements in quality of life.