Objective We aimed to explore whether nursing professionals’ psychological states affect their grief response for a patient’s death in the coronavirus disease-2019 (COVID-19) inpatients’ ward. Methods Survey was conducted among frontline nursing professionals working in COVID-19 inpatients wards at three tertiary-level affiliated hospitals of the University of Ulsan during April 7–26, 2022. Participants’ information such as age, years of employment, or marital status were collected, and their responses to rating scales including Pandemic Grief Scale (PGS) for healthcare workers, Stress and Anxiety to Viral Epidemics-9 items (SAVE-9), Patient Health Questionnaire-9 (PHQ-9), Loneliness and Social Isolation Scale, and Insomnia Severity Scale (ISI) were collected. Results All 251 responses were analyzed. We observed that 34% reportedly suffered from depression. The linear regression analysis showed that a high PGS score was expected by high SAVE-9 (β=0.12, p=0.040), high PHQ-9 (β=0.25, p<0.001), high loneliness (β=0.17, p=0.006), and high ISI score (β=0.16, p=0.006, F=20.05, p<0.001). The mediation analysis showed that the depression of nursing professionals directly influenced their pandemic grief reaction, and their work-related stress and viral anxiety, insomnia severity, and loneliness partially mediated the association. Conclusion We confirm that frontline nursing professionals’ depression directly influenced their grief reaction, and their work-related stress and viral anxiety, insomnia severity, and loneliness partially mediated the association. We hope to establish a psychological and social support system for the mental health of nurses working in the COVID-19 wards.