Background: Emergency department nurses often work in challenging workplace situations, which can cause mental health issues such as depression and post-traumatic stress symptoms that, as a sequence, negatively impact their personal and professional well-being. The eye movement desensitization and reprocessing (EMDR) technique is a structured therapy that facilitates healing from emotional disturbance caused by distressful life experiences. So, the aim of this study was to evaluate the effect of eye movement desensitization and reprocessing technique on depression and post-traumatic stress symptoms among emergency nurses. This study was carried out using a quasi-experimental design at the Emergency Departments of Accidents Hospital, Obstetrics and Gynecology Hospital, and Pediatrics Hospital at Zagazig University Hospitals, Sharkia Governorate, Egypt. The study included a sample of seventy-five emergency nurses who met the inclusion criteria. The study’s data were collected using the following tools: a structured interview questionnaire composed of two parts (a demographic data sheet and a work data sheet), the Beck Depression Inventory-Second Edition (BDI-II), and the Post-Traumatic Stress Disorder Checklist for the DSM-5 (PCL-5). Results: The findings of this study showed highly significant improvement (p < 0.0001) in levels and mean scores of depression as well as post-traumatic stress symptoms after application of the EMDR technique compared with pre-application of the EMDR technique. Conclusions: Eye movement desensitization and reprocessing technique was effective in reducing depression and post-traumatic stress symptoms among emergency nurses. Therefore, it is recommended to replicate the study using a larger probability sample of nursing staff from different areas of hospitals to help for generalization of the results and confirm the effectiveness of eye movement desensitization and reprocessing technique.