Substance use is common among military personnel and war veterans, especially combat veterans. In the last decade, moral injury (MI) has emerged as a shame and guilt-based trauma-related syndrome which may emerge among war veterans engaging in potentially morally injurious events (PMIEs). However, up to date, research has focused on the association between MI and alcohol, neglecting other substances, and little is known about additional psychological factors which may mediate the association between MI and substance use. In this study, 191 Israeli combat veterans (85.4% men, mean age=25.39) completed a set of validated self-report questionnaires. Results indicated that across all substances, prevalence rates of use reported by Israeli veterans were significantly higher compared to those reported among the general population. A serial mediation analysis indicated that the association between levels of perceived betrayal and frequency of cannabis and sedative/tranquilizer use was mediated by levels of psychological distress. In addition, the association between levels of perceived perpetration and frequency of cannabis and sedative/tranquilizer use was mediated by levels of distress and perceived social support. Notably, the association between levels of perceived perpetration and frequency of alcohol use was mediated by high level of perceived social support. We conclude that perceived social support may play a unique role in the link between PMIEs and the use of different substances, serving alternately as both a protective and risk factor.