There is consensus that military personnel can encounter a far more diverse set of challenges than researchers and clinicians have historically appreciated. Moral injury (MI) represents an emerging construct to capture behavioural, social, and spiritual suffering that may transcend and overlap with mental health diagnoses (e.g., post-traumatic stress disorder and major depressive disorder). The Expressions of Moral Injury Scale-Military Version (EMIS-M) was developed to provide a reliable and valid means for assessing the warning signs of a MI in military populations. Drawing on independent samples of veterans who had served in a war-zone environment, factor analytic results revealed 2 distinct factors related to MI expressions directed at both self (9 items) and others (8 items). These subscales generated excellent internal consistency and temporal stability over a 6-month period. When compared to measures of post-traumatic stress disorder, major depressive disorder, and other theoretically relevant constructs (e.g., forgiveness, social support, moral emotions, and combat exposure), EMIS-M scores demonstrated strong convergent, divergent, and incremental validity. In addition, although structural equation modelling findings supported a possible general MI factor in Study 2, the patterns of associations for self- and other-directed expressions yielded evidence for differential validity with varying forms of forgiveness and combat exposure. As such, the EMIS-M provides a face valid, psychometrically validated tool for assessing expressions of apparent MI subtypes in research and clinical settings. Looking ahead, the EMIS-M will hopefully advance the scientific understanding of MI while supporting innovation for clinicians to tailor evidence-based treatments and/or develop novel approaches for addressing MI in their work.