AimAmidst the COVID‐19 pandemic, the association between organizational justice and psychological distress among hospital nursing staff is underexplored. Thus, this cross‐sectional study, conducted in Fukuoka Prefecture, Japan, examined the relationship between organizational justice and serious psychological distress (SPD) among hospital nursing staff during COVID‐19.MethodsThe study surveyed 783 hospital nursing staff using the Organizational Justice Questionnaire and Effort‐Reward Imbalance Questionnaire. The Kessler K6 scale was used to measure SPD. Sociodemographic and occupational characteristics were controlled for as potential confounders.ResultsThe prevalence of SPD was 14.4%, with a mean K6 score of 6.5. Moderate procedural justice (odds ratio [OR] = 2.38, 95% confidence interval [CI] = 1.14–4.94, p = .021) and low distributive justice (effort‐reward imbalance) (OR = 3.66, 95% CI = 2.01–6.67, p < .001) were associated with SPD, even after adjustment for confounders. Interactional justice showed significance only in the crude model. Effort‐reward imbalance had the strongest association with SPD.ConclusionsThe findings showed that moderate procedural justice and low distributive justice were associated with SPD, highlighting the need for organizational interventions to address these factors. Imbalances in effort/reward had the greatest impact, highlighting the critical role of distributive justice in mental health. Thus, in the context of a pandemic, extreme procedural justice is not necessarily associated with mental health, and efforts to ensure distributive justice are critical to improving the mental health of hospital nursing staff. Moreover, organizational stressors should be addressed during disruptive conditions such as infectious disease outbreaks.