Research focused on elucidating moral injury amongst healthcare workers (HCWs) is essential due to the deep connection with morality and individuals’ overall wellbeing. Examining moral injury provides an avenue through which researchers can connect individual experiences with systemic level causes (i.e., structural power imbalances between clinicians and health systems) to better study workplace wellbeing. The omnipresence of the COVID-19 pandemic has amplified the need to study moral injury. This paper describes a systematic review conducted using PRISMA-P guidelines to answer the question, “what is the association between moral injury and professional wellbeing and mental health amongst healthcare workers.” Twelve databases were searched to identify specified studies. This study’s criteria included: (1) articles published through December 2022; (2) qualitative and quantitative empirical studies; (3) articles written in English; (4) articles including moral injury; and (5) articles including at minimum one other measure of professional or personal wellbeing. The initial search produced 248 articles, and 18 articles were ultimately included in the final review. To confirm that no articles were left out of this study, the first author of each included article was contacted to inquire about any additional works that met the inclusion criteria of this study. The elements of the 18 included articles described in this review are discussed. The results indicate that moral injury is associated with both professional wellbeing factors and mental health outcomes. Further theoretical development, including (professional- and identity-based) exploratory research on moral injury, and evidenced-based interventions for moral injury are needed.