AimThis cross‐sectional study aimed to investigate the factors that affected the mental health of Korean nurses caring for coronavirus disease 2019 (COVID‐19) patients, causing posttraumatic stress disorder, depression, anxiety, and sleep disorders.BackgroundInfectious disease outbreaks like COVID‐19 affect the mental health not only of those who contract the disease but also of nurses caring for affected patients.IntroductionTo address health issues effectively, it is essential to comprehend how to prevent them. Therefore, it is necessary to scrutinize the origins of COVID‐19–related health concerns and devise measures to prevent potential problems.MethodWe used an online survey to collect data from 136 nurses caring for COVID‐19 patients during the initial stage of the pandemic. The data were analyzed using the one‐way analysis of variance and a simple logistic regression.ResultsThe findings confirmed a high prevalence of posttraumatic stress disorder among nurses, with symptoms of depression, anxiety, and sleep problems.DiscussionOur research has shown that it is important not to exacerbate the difficulties that nurses face after their activities. Therefore, it proposes for creating environmental structures that mitigate predictable challenges such as workload from various tasks, sleep disturbances, and hopelessness, rather than focusing on personal vulnerabilities.ConclusionTimely attention to influencing factors can reduce the risk to nurses' mental health, so we need to plan preventive measures that reflect the influencing factors to prepare for future pandemics.Implications for nursing and health policyContinuous monitoring of the mental health status of nurses responding to a global health crisis and the development of appropriate psychological support programs and policies for creating a conducive work environment are necessary.