The Irish Defense Forces (DF) responded to the COVID-19 pandemic and national public health crisis by deploying personnel to aid domestic civil authorities in medical and care settings, contact tracing, logistics, and operations. Current research on COVID-19 reveals increased psychological distress among frontline workers and the general public. Resilience has previously been associated with lower levels of psychological distress. This study sets out to test these associations, and to examine mental health differences between DF personnel deployed in Ireland on pandemic-related duties (DIPD) and non-DIPD. Participants were 231 DF members who completed the: Connor-Davidson Resilience Scale-10, Patient Health Questionnaire-9, Generalized Anxiety Disorder-7, Perceived Coronavirus Threat Questionnaire, Brief Trauma Questionnaire, Post-traumatic Stress Disorder Checklist-5, and Alcohol Use Disorder Identification Test. Independent t -tests revealed no differences between DIPD and non-DIPD on measures of psychological distress or on self-rated mental health prior to COVID-19 (PC19) and during COVID-19 (DC19). Results of multiple hierarchical regression analyses revealed that depression predicted lower levels of resilience, while multiple traumatic events predicted higher levels of resilience. The total adjusted variance explained by the model was 25%. Clinical and policy implications for improving access to psychological support within the DF and military populations are discussed.